Hehe, I'm still laughing from funny posts I saw. One was about Enchanting/Engineering, lol. That's pretty funny. If you do any profession, you really need to choose the respective gathering profession to go along with it, unless of course you do Tailoring/Alchemy, since cloth drops off mobs and you can buy the other random materials you need. Otherwise, you absolutely must pick a manufacturing/gathering profession or you will lose money and it won't be worth it. Do NOT do Engineering/Enchanting, that's the single worst idea I've ever heard of. Sorry for flaming, but I don't want you to gimp your character by wasting money like this.
As for what profession I chose. This was difficult. Rogues really have three very viable choices. There's Skinning/Leatherworking, Herbalism/Alchemy, and Mining/Engineering. All of the other possible combinations really don't help a rogue out too much.
Skinning/Leatherworking is great because you can make very good armor with it. Having upgraded armor is always a good thing and both PvP and PvE. However, this combo will not have a profoud nor noticeable effect on your battles. You will gain an advantage from having updated armor with +stats and AC, but it is not really noticable nor is it flashy.
Alchemy/Herbalism is an excellent choice for any class in this game. Healing potions are probably the most used items in the game, and for good reason; an extra 600 health from a lvl 110 recipe is a big boost, especially isnce it is instant, and your enemy has no idea you have it. I would never recommend against this combination, as it's easy for new players, very easy to take advantage of, and herbalism is a simple gathering profession.
Last is engineering/mining. This is the profession I chose, because engineers have many gadgets available to them. New players wouldn't and shouldn't ever choose this profession, as it involves the most complicated gathering skill, and the second most complicated manufacturing skill (enchanting is the most complicated). However, a rogue gains many benefits from this profession. Goggle are cool, and are worn on the head, so having them when you need a good headset is certainly an excelent thing. AoE stun effects from grenades and bombs are by no means battle changing, but they can do some extra damage to a good group of enemies, as well as disorient them for a few crucial seconds. Guns/ scope, and bullets help b/c they are valuable to other players and you can even do decent damage with them at range yourself. Last, engineering is wayyy cool. Mechanical Dragonlings, Gnomish Battle Chicken, and, the all powerful, Gnomish Net-o-Matic. Rogues have no real snare technique and this one seals the deal. Very annoying when you're snared by a rogue, because you're dead. Anyway, thanks for reading, and enjoy this amazing game.
Make love, not war.