It is pointless to kill Roibeard until you have reached level 50 and you have received the quest to kill the named dude across the road from Roibeard. The named dude across the road has the orders concerning the Jewel Of Ice. Until you have found those orders and turned them in Roibeard drops nothing. I killed him half a dozen times before I decided to wait and see what happened in the quest tree.
Edited, Sep 20th 2011 3:22pm by bwhorn