Acid Mages are the acid-based counterpart of flame/ice/electric mages. They specialize in acid spells, and both they and their starting pet are acid resistant. Starting with a wand of acid, they can blast nasty enemies but unlike flame/electric mages cannot burn permanent Elbereths, making them a bit harder to play.
Barbarians have their usual strong starting physical stats and intrinsic poison resistance, making their early game easier than most. However, Barbarians are charged three times as much money in shops, which pairs poorly with their low starting charisma. Unfortunately, their guaranteed sacrifice gift Cleaver is a bit underwhelming past the early/mid-game, so Barbarians will want to aim for stronger weapons eventually.
Bards are a hard role with very weak starting equipment. Their lack of a starting weapon is a problem that should be corrected by finding a suitable weapon ASAP, and their wooden/tin instruments won't be of much use either. When leveling up, bards gain certain spellbooks that can come in handy.
Chefs get permanent food appraisal. Plus, chefs gain fire and poison resistance when they level up. However, their starting knife won't likely take them very far, and they suffer from a lack of decent weapon skills. Their skill scales as the game goes on due to their powerful artifact weapon options from sacrifice and their quest artifact The Deluxe Yendorian Knife.
Convicts are a harder-than-hard role that starts with a heavy iron ball chained to the player, a cursed striped shirt and negative alignment and luck. Races that would usually be peaceful will be hostile to the Convict. Shopkeepers who see their striped shirt will not allow them into their shop, and watchmen as well as vault guards will attack them on sight.
Corsairs don't particularly excel at anything but don't suffer from serious drawbacks either; their starting equipment includes an oilskin sack as well as a good stack of daggers.
Divers don't particularly excel at anything but don't suffer from serious drawbacks either; their starting equipment includes an oilskin cloak and a can of grease, along with some spears and trident.
Drunks benefit from quaffing booze and can always make more, but they also start with a large stack of random potions that may be full healing or other useful types. Other than that they get nothing special, and their starting weapon is particularly crappy, so they'll need to luck into finding good equipment or they'll have a hard time.
Electric Mages are the lightning-based counterpart of flame/ice/acid mages. They specialize in shock spells, and both they and their starting pet are shock resistant. Starting with a wand of lightning, they can easily survive the early game by burning a permanent Elbereth in critical situations.
Firefighters should be relatively safe early on due to their wand of fire which can burn Elbereths. Their starting stack of water is just waiting for an altar that allows converting it to holy water, so either a dip into Minetown or an early altar conversion are early targets. The Firefighter's starting axe is not the strongest weapon but they can advance a large variety of other weapon skills.
Geeks were renamed from the previous role Graduate. They start with wacky equipment and may have a difficult time getting off the ground. However, their starting pencil can be used to engrave without dulling, and the expensive camera can be a useful utility item.
Gladiators starting equipment includes a shield of reflection though and a silver spear, both of which are strong items if they can complement them with items found in the dungeon early on.
Hackers were renamed from the previous role Geek. They have a unique starting inventory that can be quite powerful if used correctly. Their electric sword is one of the best one-handed weapons in the game, which can sometimes even apply additional shock damage against monsters. Their ICs can be sold for a solid amount of money, that can either be used for purchasing additional items in shops or buying protection. Their Jolt Cola, when blessed, have a small chance of increasing their level and can give a slight boost to their maximum hitpoints. Their Hacker's Foods also prevent them from starving too easily.
Healers now start with a wand of healing and medical kit in exchange for giving up the spellbook of extra healing. Their sacrifice gift, Mirrorbright, adds to their defensive prowess - but this still leaves Healers with the same dependence on obtaining a powerful artifact weapon that can deal adequate damage to complement this.
Jedi use lightsabers and have techniques to recharge them, move objects from a distance and do jumps. They can't get proficient at most other types of weapons though, and they either run out of lightsaber energy often or have to use a turn every time a monster shows up to turn their saber back on.
Knights start with -3 AC worth of heavy armor, helping out their early game significantly. They also start with many more apples and carrots, allowing them to keep their pet horse fed much more easily. Praying for minions is an effective strategy for knights, and is a viable consideration at almost every phase of the game.
Locksmiths start the game with no weapon and only a lowly dagger, and their (un)locking tools and wands won't help much in an actual combat situation so they need to turn up useful equipment quickly or they won't stand a chance. They're likely to have to rely on their starting pet for quite some time and engrave Elbereth often.
Lunatics are a role-specific version of the Lycanthrope race. The player either has to find a way to control their random transformations or accept not always being able to wear/wield armor and weapons.
Monks have a strong early game assisted by their sacrifice gift, the Gauntlets of Defense. Coupled with tactical usage of their assorted techniques - such as the chained blitz that deals massive damage when used correctly - monks are one of the strongest roles.
Musicians can use their magic harp to turn dangerous monsters into powerful alies, and their other instruments (including a drum of earthquake) may also be useful at times. They don't start with an actual weapon though, so they should try to find one quickly. If they manage to get surrounded by several strong monsters and tame them all at once with their harp they may be quite able to survive the early game.
Necromancers are glass cannons, having a similar starting inventory and stats to a wizard with the added benefit of detecting the beatitude of items like a Priest. Their power scales as the game progresses, with their sacrifice gift being Serpent's Tongue, an endgame-caliber weapon. Their quest artifact, The Great Dagger of Glaurgnaa is a nice boon, providing rare slotless magic resistance and the ability to invoke for an energy boost. Moreover, their starting sickness resistance and drain resistance pay increasing dividends as the game progresses.
Officers start with a pistol and some useful wands, which can be doubled by their starting pet that starts with the same items and immediately drops them on their first turn. This allows the Officer to dual-wield pistols from the start and gun down any dangerous enemies with the downside of doing poor melee damage. Still, it's probably better than whacking enemies with a club that doesn't do any meaningful damage either, and may allow the Officer to survive long enough to find another useful weapon. Dual-wielding with a pistol in main hand and a strong melee weapon (e.g. silver saber) in the other hand enables the player to do well in both melee and ranged combat without having to switch weapons.
Paladins are basically enhanced knights who also get undead warning and demon warning, but their code of conduct is much harsher, giving larger penalties than the knight conduct. However, the paladin's starting equipment is also better than the knight's, and they have a higher chance of successfully casting difficult spells.
Priests/Priestesses have not changed significantly, and their early game suffers slightly due to the variety of early-game threats added. Their sacrifice gift is Disrupter, which has solid situational use, but are of limited use against said early-game monsters. However, Disruptor is a great boon against the many strong undead spellcasters both new and returning, and as such is worth keeping and enchanting in order to overcome enchantment resistances.
Rangers are largely unchanged, with their sacrifice gift being decent improvements on their starting dagger and bow. However, SlashTHEM encourages rangers to use ranged weapons as their primary offense, with more bonuses to multishot. As a result, retaining the starting stack of arrows is more important, and obtaining holy water and the Mine's End luckstone are early priorities.
Rogues' first priority is almost certainly sacrificing for the uber-strong Bat from Hell. Once obtained, pretty much the only thing that can take out a Rogue in the early/middle game is hubris. Rogues are even better equipped to steal money, now with scrolls of gold detection and teleportation suited for plundering vaults in addition to their oilskin sack to steal items and money from shops.
Samurai have the option to either go for Kiku-ichimonj or Excalibur if lawful. Both of these weapons have a strong additional damage bonus making them strong choices, on top of Excalibur's important drain resistance.
Tourists have access to Whisperfeet, but are still quite fragile. Like vanilla, their power does not scale as much until later in the game once they can obtain the Platinum Yendorian Express Card and the wand of wishing. Doppelgangers can make up for the weak starting stats and equipment with careful use of polyforms.
Undertakers begin the game with a pitiful scalpel that should be ditched for a real melee weapon, and they can turn undead both by using the technique and zapping the wand of undead turning so they may be able to resurrect a fallen pet. Unless they luck into good equipment, they'll probably need to use pets in order to survive the early game.
Valkyries are strong fighters as always, exchanging their long sword for a spear, and their +3 small shield is still one of the most powerful starting pieces of armor for any role. Their sacrifice gift, Mjollnir, remains extremely powerful and deals almost twice as much electric damage on average. While the Valkyrie quest artifact, the Orb of Fate, is somewhat overshadowed by the lighter Hand of Vecna, it still has useful properties such as half spell damage and levelport capabilities.
Warriors are great at using melee weapons and good at ranged combat too, but they can't learn any spellcasting skills. The warrior starts with a nice set of armor and weapons, giving them a straightforward early game. Their main difficulty is beating the Quest, thanks to their nemesis basically being a buffed Master Kaen.
Wizards now start with four spellbooks, but have a much harder time than in vanilla. Even after obtaining Magicbane, they are fragile especially with the addition of difficult early threats. What's more, wizards will likely find themselves strapped for item slots for extrinsics.
Zookeepers start with three blessed scrolls of taming, allowing them to turn dangerous monsters into pets. They also get tripe rations and leashes which further aids them in gaining and maintaining pets, but their taming scrolls will only last so long. The player should make the most out of them. Confusion may allow the scrolls to tame a much bigger amount of monsters, turning them against the ones that resist. Zookeepers will want to find better armor and weapons if they want to survive early on.