WoW has evolved heavily over the years, and one of the gradual changes has been a reduction in the importance of choosing your profession carefully. In Vanilla WoW, tailoring was almost a necessity for any priest gearing up for endgame, and TBC brought us the stunheralding warrior blacksmiths (I still have nightmares). WotLK has killed a lot of the variation with professions as there are pretty much no BoP craftable items worth bothering with.
Despite the lack of variety that professions once gave, they still still make a difference to your game. Their bonuses come in the form of gear enhancements for the crafting professions, and passive bonuses/skills for the gathering professions. For anyone considering levelling a rogue, here's a quick breakdown of the available professions and the bonuses they give in a PVP environment.
|Alchemy||+80ap||Flask of the North|
|Black Smithing||+80ap||Socket Bracer + Socket Gloves*|
|Enchanting||+80ap||Two 40ap ring enchants|
|Engineering||-44ap, 1654-2020 dmg||Pyro Rockets|
|Inscription||+80ap||Inscription of the Axe|
|Jewel Crafting||+84ap||Three 68ap gems|
|Leather Working||+80ap||wrist lining|
|Tailoring||400ap proc||Swordguard Embroidery|
* Stacks with other enchants
|Herbalism||3600 heal||3min CD|
|Skinning||+0.54% Crit||Master of Anatomy|
None of the professions are terrible (you might want to avoid Mining) but it's worth considering Engineering. The glove enchant comes at the cost of 44ap, but hits reasonably hard and is great for keeping enemy players in combat if they're trying to escape (as well as hitting through Hand of Protection. Hypervision Goggles are worth considering as well if you're struggling vs other rogue teams (more on that here).
If you're just after raw stats, Jewel Crafting still comes out on top even though it lost a lot of its initial appeal (BoP prismatic gems no longer count as blue/red/yellow). The proc from the Tailoring 'enchant' is worth a look as well (think of it as another Berserking proc), but it does mean losing Shadow Armor.