Here is a video outlining a powerful and usable Rift rogue assassin build. You can play this character build regardless of whether you are Guardian or Defiant. If you are a low level rogue and have not yet picked a specialization path or build then I would highly recommend that you try the assassin. It is a great fun build to play as, and I am sure you will enjoy it. The video also has some level 50 gameplay footage of various characters, just to give you a goal to work towards.
If you want to hit level 50 quickly, or you want to learn more about how to build a strong Rogue/assassin, check out this Rift build and leveling guide.
If you are serious about Rift then click here for an in-depth Rift classes, builds, and quests guide.