After taking care of the snake I would be on a man hunt to find out who did it. I would hand the roommate the bill and tell him if he didnt want to pay the bill find out who did it. If he refuses to pay hes an ass and a bad roommate who dosent respect your property. He invited people over he's responsable for the place and any damage done by his friends to your stuff.
I would find a new roommate, but before he moves out have a party and trash some of his stuff and refuse to pay so he gets the point. Thats just me though.