First of all, not all insurance companies cover roommates. You also need to explicitly add your roommates to your policy. Normally, insurance companies allow you to add 1-3 roommates per policy. Some insurance companies don't allow adding any roomate. Your claims can be denied if your roommate is not added before you file the claims.
The information in this answer is general in nature and is not legal or insurance advice for your specific situation. Policy language varies carrier by carrier; your declarations page is the final word. If you're unsure, call your agent before you need to file.