Talk to the problem roommate. Approach the roommate when it is convenient for both of you to have a frank discussion. To soften the blow, tell him of the nice things you enjoyed about living with him. Then tell him very frankly about the issues that mean he can no longer live there. Emphasize the issues lie not with him but with a conflicting lifestyle. Do not blame the person; blame the behavior. Remain calm even if the other person is not. Come prepared with notes of specific times and dates of behavior or actions that are leading up to this conversation. If the issue escalates to court, the person with documentation always wins.