Is it possible that you can find out if an inmate has a roommate without them having to be the one who tells you?
You can call the facility and ask them. They are not supposed to share anything about the inmate's actions inside the facility, including their cellie. If you get one that you can get to know (a counselor or unit secretary), you might talk them into giving little tidbits about the inmate, but it's a rule-breaker if they do. Most state prisons have 2-3 people per cell. If you get lucky enough not to have a roommate, then that wouldn't be too bad.
People have asked similar-type questions like; if they can get information on who is on the inmate's visiting list? NO; can i know how much money is on their books? NO; can i know who is on their phone list? NO;