I have a room mate who signed the lease with me saying that he is going to move out with his girlfriend. I don't want this to affect me in any way but I see no why where that wouldn't happen.

My room mate recently decided he wanted to move out with his girlfriend and we have about another 6 months left on our lease. We both signed it so we would both be responsible for the place, and now that he is moving out I don't want to be responsible for this crappy situation he is leaving me in. I can't pay the entire thing by myself every month, so I absolutely need a room mate. Is there any way that I can get him off the lease without terminating the contract (they expedite all the payments and I'd have to pay all 6 months then and there) or anything I can do to him without it affecting me also?