1. You can use Pickpocket for at least one Quest. In Beta you were able to steal a specific amount of Weight ( depending on your Skilllevel ). But havent used a Rogue in Release.

2. Without Backstab they are Weak yes, but if you Backstab they are nearly as strong as Two Handed Weapons but only use half the Ap/Attack. Thanks to this you are able to kill things really fast.
Also you can use Daggers for CC. Since they only need 2Ap/Attack you can use Daggers with Chill or Petrify and Stunlock Enemies.

3. Bows and Crossbows are equal if not even stronger than Magic. The only downside is that you will use up Special Arrows. A good Strategy is using Bows on Range like a Mage ( still nearly as strong ) and switching to Daggers after 1-2 Round when the Enemies come Closer and deal Damage like a Two Handed Warrior ( or even more ).