Theres no particular rotation.. its pvp - there is a matter of priorities though. Get Unstable Affliction up as soon as possible for the dispell protection it grants, obviously if you cant stand still and cast it then just use your instant spells until you can cast. Haunt should also be high priority due to its nature - plus the nice heal it gives other than that, Corruption, Bane of Agony, and a curse. Melee generally elements or exhaustion, Caster generally Elements or Tongues. Use Drain life as the general filler, Fel flame if running about. ShadowFlame when they are close to slow them even more.
Rogues kill Warlocks, get used to it :P - sorry to say it mate but if you win against a rogue at your current skill level, then the rogue was shockingly bad =/
well it isnt so much a rotation in pvp, as much as a priority depending on whats happening at the time, just keep all your dots up on the target and drain life i'd say (dont do much pvp)
For rogues, well theyre tough to kill at the best of times, but a tip ive learned to use is to summon your voidwalker and get him to use "Consume Shadows" this gives you greatly increased stealth detection, and quite often you can pick them out of stealth with a dot. Hope this helps.