A roommate not on the lease generally makes you the landlord and the roommate the subtenant. We wrote a comprehensive guide on roommate eviction that you can find here: https://www.robinsonandhenry.com/colorado/real-estate/roommate-evictions/. If you would like to speak to our eviction team about the specifics of your case please contact us at (303) 688-0944 or go to https://www.robinsonandhenry.com/locations/ for more contact options. It is important that you do not use self-help remedies such as changing the locks without going through the eviction process.