Enchanting is one of the most importamt professions that help you for PvP, besides, others are Jewel Crafting, Engineering, and Blacksmithing. To large scale Blacksmithing is the weakest of these professions, but it will give you a jumpstart while gearing your rogue from scratch. In the long run, the blacksmithing weapons have already been outpaced by arena gear, so I don't recommend this. Right now Jewel Crafting and Enchanting are the best arena professions because of the extra stats they give you. However, Engineering is great for world PvP, duels, and BGs and is due for a buff.
   Enchanting: You get to add either +4 all stats OR +2 weapon damage on each of your rings. Being able to disenchant is also really nice for making gold, but it doesn't affect PvP.
Jewel Crafting: You get access to a couple epic unique BoP gems. The useful ones for a Rogue are currently one 24ap gem and one 18 stam gem. From what I've seen there may be more of these gems coming out in the future as well. In addition, you can get the Nightseye Panther trinket  This is a really nice trinket as it is useable in stealth and gives you +5 stealth.
Engineering: Lots of fun stuff, but mostly unhelpful for arena. The Goblin Rocket Launcher is a nice trinket and useable in arena, but its cast time is interrupted by any damage so it's only really useful for 1eve1 other than the 45 passive stamina in part. The Gnomish counterpart is not useable in arena. The stealth detection goggles are useful, but since gear swapping has been disabled in arena because of crybaby Warlocks, it's hard to take advantage of them in arena. The Nigh Invulnerability Belt is useable in arena, and is very powerful when it doesn't backfire. And I guess the Deathblow Goggles are worth a mention as they are on par with the season 2 helm and can save you some arena points as you gear up
You can't go wrong picking any 2 of those 3 professions for PvP. Whatever floats your boat. Personally, I would take Engineering and then choose between Jewel Crafting and Enchanting.
TBC has made gear decisions pretty simple for PvPers. In fact, there are no decisions. You just gather all the PvP gear as efficiently as possible. The way you do this will depend on how hardcore you are when it comes to honor farming. After that any extra honor I could muster would go toward the season 1 weapons, and then toward season 1 arena gear. If you don't mind farming honor, you might want to get the weapons first, because you probably won't be upgrading them for a while.
Make sure you start doing arena as soon as you hit 70. Even with ratings, there is a big difference between 300 points per week. The first piece of gear you should buy is the gloves. They are the cheapest piece and the deadly throw bonus on them is a must have. After that, the legs, chest, and helm are the best pieces stat-wise. So get them in whatever order replaces your worst items first. Hit rating caps are at 5% for specials, after that it only affects your white damage. So the first 79 hit rating that you get are the most valuable stats you can pick up.