Envenom with the build that is in the related links
Balance, go with all zee balance thingys.
Shadow Rouge is better for PVP, Combat Rouge is better for PVE. So depends on what you wanna do more of.
It depends what you want to do. For PvP, I find a destro/demonology build best, but if raiding an affliction/demonology build is brilliant.
It depends on how you play, there are pvp builds for all 3 of them as well as raiding builds for all 3 of them. If you have a spec that you like you should go to a website that shows you the best rotation for that spec for raiding or pvp and which stats you should have and what stats you shouldn't have.
Demo for raid utility during 25 man raids for the sp buff. Destro for large hits and PvP Aff is currently the highest dps build, and used for long boss fights and PvP as well.
VCN is Best PVP BG ARENA SERVER
There are many websites and resources that offer instructions on how to setup and install PVP software. The best website to get instructions on installation is the PVP website.
officion newbie
For PVP, I wouldn't recommend combat. (High immediate burst damage, but not great for being all stealthy and sneaky). Most PVP rogues want to stunlock, which means subtlety or assassination. As assassination has a more "even spread" of abilities (sneaky and open damage), it's common in PVP and PVE (and it's what I play as). However if you really want to bring people down in PVP i'd go with subtlety. Did I say bring people down? I meant have them nailed to the spot as you slice them to bits with daggers.
Sylvanas
depends on your spec and purpose pvp ambush will need a slow dagger in the main hand but a assassination would like some faster ones pve (raid) combat will like the slowest possible dagger for the windfury proc
Rogues are DPS - Damage per second, class - in PVE (player versus environment) you want control over the mob and the ability to run away if things go badly. In PVP, everything is always going badly so you can't run away. but you can outlast and outdamage your opponent, so the idea is to setup crit and instant high damage attacks (nothing "over time" or DOTs) - pump and dump. Combat is a good spec, but there is no ONE talent that is only for PVP. The most useful on I've seen is Cheap Shot. It disables a mob, it does damage and allows you to get behind them to do extra damage: Stun Lock FTW!