Before we got married my wife found some decent roommates via the message board here.
http://www.frontline.to/cgi-bin/ultimatebb.cgi
Frontline is the singles group at McLean Bible Church, just FYI. Her roommates weren't Bible thumpers by any means. They were actually pretty laid back. Anyways, I think it could be a good place to find decent roommates who wouldn't be much trouble. Unless you're looking for trouble of course...
Finding roommates is a crapshoot though. When we were looking to fill a spot in our Townhouse we posted on Frontline and on Craigslist and didn't see a whole lot of cool ppl responding to the post. Finally found a roommate through word of mouth, a recent graduate from our alma mater. So you might consider etting your college alumni coordinator know...