I swear I heard his voice during thieves guild at least two times.


http://www.youtube.com/watch?feature=player_detailpage&v=V3X2Ojde5yI#t=152s

http://www.youtube.com/watch?feature=player_detailpage&v=YqX8ncqGaM0#t=52s

He does indeed voice a number of characters in Skyrim.

While I have yet to do the quest lines leading up to anything he voices, I am now REALLY looking forward to doing so.

Here's a link for proof (just search for his name):
http://www.uesp.net/wiki/Skyrim:Voice_Actors