The law does not remover your right to privacy because your "roommate" is on probation. However, her rights are reduced. A probation officer could search any part of the residence to which she has access. Putting a lock on your door and locking it regularly when you are out of the room is an excellent way of demonstrating your right to privacy in what is in your room.
I agree entirely with the other answer. Since you know that there may be searches, however, I would suggest that you make certain not to have anything anywhere in the house - even in your locked, private room - that is illegal. Why take any chances?
They can search common areas and areas the felon has access to so if you want to be private, lock it up and don't allow access, ever.