Legal Question in Criminal Law in California

First of all, the probationer must have a search clause. Not everyone on probation is searchable.

A probation search generally includes the probationer's room, all common areas of the house, and all areas accessible to them. By living with someone on searchable probation, you have a reduced expectation of privacy.

If you don't want your room searched, you should put a lock on the door and make sure the probationer doesn't have access to a key.