Warrior: Tanking is permanently in demand, since it’s a less glorified role until later expansions. While leveling sucks due to stat dependency that can’t be sated until 50s+, they are good all around at level cap. While they’re a poor solo class (soloing some of those Silithus elites is annoying), they’re great when assisted.
DPS is top tier, and they have strong cleave, though weak AoE. Protection is solid for tanking with low gear before Fury/Prot becomes a thing, and you can effectively DPS without being full Fury (or Arms). You can also spec 31/5/15 for an Arms tanking build to also use a 2h, so you can PvP well and tank okay, though you won’t be specializing here.
If you choose warrior: Get a swing timer, so you can monitor your rage. I also advise leveling as Arms or Fury; the debate on which is better depends on how you choose to level. Fury mows down green mobs, and Arms is pretty worthless before Sweeping Strikes (and arguably Whirlwind at 36, or Mortal Strike at 40). The math says they’re equal at lower levels, with Fury being potentially better when fighting lower mobs. I leveled Fury from start to finish, and it wasn’t bad at all, but you’ll get irritated by the parries and misses. You can actually go into Arms and dual wield (spec doesn’t matter early for DW) to get Improved Overpower, Impale, and Tactical Mastery. With DW, you will have more hits to get dodged for the sweet Overpower crits (additionally more powerful by Impale).
Rogue is… eh. Cooldown-centric in classic for huge power spikes. They’re safe and versatile, and get a LOT of free melee stats in Combat. But they aren’t special at low levels, and you have gear competition against hunters and warriors in many, many cases. Nowadays, raiders are plenty geared, though, so it should be much friendlier. In a warrior’s case, tanking plate is automatic to them, though.
For both classes, you want to farm a Hand of Justice, which sucks. Rogues can solo it with enough gear, but not a warrior. Warriors can (thankfully) skip SGC nowadays with ZG, and the advent of AQ opening.