Second, did you have your roommate SERVED with the necessary notice to QUIT? ( By an independent process server, or at least someone other than yourself?)
If you DO change the locks, without undergoing legal due process, SHE will be the one with legal grounds - probably - to have the Sheriff pay YOU a visit, to retrieve a key - for her - to the new locks.
As you might suspect, it's NOT as easy to get OUT, as it was to get INTO the situation, and you'd best step carefully, and dare I add, cordially, because she probably DOES have some rights, if she chooses to enforce them.
If it's your house I think you can change the lock anytime you feel the need, but restricting her things and access might be a problem.