Silly writer, blacksmithing is for warriors! Not anymore. Sure, it'll suck to level it up, going through tons of valuable materials to create worthless plate armor -- but when you get up to the Burning Crusade levels, the profession starts shining.
There are a few decent BOE rogue items that require Primal Nethers, so it's much easier to get them as a blacksmith yourself (Dirge, Felsteel Reaper, and Runic Hammer.) The Adamantite Sharpening Stone and Adamantite Weightstone come in handy when you're fighting poison-immune bosses or elementals. But the real treasures here are the upgradeable BOE swords and maces. The swords (Fireguard, Blazeguard and Blazefury) are excellent, quick offhands that will last you a long time, while the maces (Drakefist Hammer, Dragonmaw and Dragonstrike) are the darling mainhands of the combat mace spec, great for PVP and decent in PVE.
I've always considered enchanting to be more of a burden than a profession. Who wants to stand around in Ironforge spamming lists of available enchants? Who wants to deal with idiots that won't tip because "you're just pressing a button"? Disenchanting, now, that's where the real fun is at. However, there's one thing that enchanters can get that no one else can -- ring enchants. Your choices are Stats or Striking. Both of these are helpful to rogues, and unlike weapons or armor, they'll never become outdated. Being an enchanter also removes some of the pain in trying to find rogue enchants, such as those discussed here and here.
Long considered the red-headed stepchild of professions, taking engineering now gives you some considerable advantages. Foremost of these is that while most blacksmithing, leatherworking, et al items are usable by everyone, nearly every engineering item requires you to be an engineer to use it. This makes it a great profession to create items for yourself and an awful profession to make money in.
Engineers can do lots of fun things, like control their enemies, turn mobs into chickens, and randomly plummet to their deaths. It's a little bit harder to find more practical engineering items, but there are some out there for rogues. The Goblin Rocket Launcher is a wonderful PvP trinket with an awesome model and a ton of stamina. Rocket Boots X-Treme combine middling rogue stats with a vicious situational use. The Gnomish Battle Goggles and Hyper-Vision Goggles are okay, but both pale next to the real reason to take engineering: the Deathblow X11 Goggles. Not difficult to make and equal to Tier 5, these goggles make all the pain and suffering of leveling engineering worth it.
In some ways, Jewelcrafting is the evil twin of Enchanting. Both professions have the potential for a lot of profit, but both require you to get rare recipes to really see money from enchanting/jewelcrafting instead of just disenchanting/prospecting. Both make it a ton easier to enhance your gear, but have very few profession-specific items. The main difference is that jewels can be sold on the AH, making the whole profession much less of a pain than enchanting. I had more fun leveling JC than any profession except alchemy, which is widely accepted to be the easiest thing to level ever.
In end-game, you can make yourself a couple of figurines, both with nice stats and side-effects. The Felsteel Boar has a great AP bonus, but its on-use isn't really good for anything except confusing your opponent in PvP. The Nightseye Panther is a little more rogue-centric, boasting an AP and stealth boost, as well as a big on-use AP shot for when the boss is at 2% and the tank is dead. There are a few epic gems available only to jewelcrafters (Crimson Sun, Falling Star, Stone of Blades), but since you can only use one of them at a time, it's not as good a bonus as you might think.
Leatherworking seems like the obvious first choice for a rogue profession. Rogues wear leather armor, and leatherworking can help them get it.
The centerpieces of rogue leathworking are the BOE Fel Skin set (gloves, boots, and leggings) and the BOP Primal Intent (bracers, belt and chestpiece.) Primal Intent focuses on AP, stam and agi, while Fel Skin helps fill in the gaps with a bit more hit and crit. The Fel Skin set is easy to get -- heck, you can even buy it off a leatherworker, or make extras to sell. The Primal Intent stuff is more difficult, as the set requires three Primal Nethers and 14 Primal Might. And if you're really, really intent on min/maxing, the excellent BOE Cobrascale pieces can be crafted by anyone lucky enough to find the extremely rare recipes.
Once you hit SSC and beyond, a few new pieces become available. The plans for the Belt of Deep Shadow and Boots of Utter Darkness both drop in SSC. And in Black Temple and Hyjal, lucky raiders can get the plans for the haste-enhancing Swiftstrike Bracers and Swiftstrike Shoulders. To make things confusing, the plans for the boots and shoulders are BOE, but the items are BOP, while the plans for the belt and bracers are BOP but create BOE items.
To enhance your new gear, consider making some Cobrahide or Nethercobra leg armor and dropping some Drums of Battle. Do it quickly! The ghosts of a thousand dead, skinless cobras are after you!
Don't take tailoring.
What profession do you think is superior for rogues? Which could stand to be buffed a little? What new rogueish items would you like to see in your profession?