When dealing with unbelievers, you need to remember that only you have the benefit of The Holy Spirit in resolving a personal conflict. The best solution in the long run is to get a Christian roomate (the Lord warns against relationships with unbelievers in order to avoid conflicts). For the time being, you want to handle this conflict the best you can, and that requires COMMUNICATION (and lots of it). PROPER AND EFFECTIVE communication means communication in NO UNCERTAIN TERMS. Have you ever wondered how a discussion becomes a HEATED discussion (argument)? When uncertain terms are used (vague, ambiguous) so that the other person is unsure of exactly what is meant and has to constantly GUESS as to what you are saying, the other person becomes frustrated and annoyed by the conversation. This is what The Holy Spirit taught me. Many times, unbelievers are also "Christian haters" and refuse to understand the Christian way of doing things, so tell your roomate you want PEACE and maybe you'll get some cooperation.