Legal Question in Real Estate Law in California

Is the roommate committing crimes or do you just want to end the roommate situation and get rid of him/her?

In the former case, calling the cops is probably appropriate.

In the latter case, no, especially if it is pretty clear that the roommate is, or can argue he/she is, a co-tenant or your sub-tenant. Paying rent (whether directly to the landlord or to you), or participating in expenses, is likely to give your roommate subtenant status. You would have to go through a formal eviction process, with written notice and all that.

Even if the roommate is a guest, not a tenant, and has worn out his/her welcome, he/she is entitled to informal notice but must leave as soon as reasonably possible before it becomes a police matter.