depending upon the contract written.
But after a point it becomes an issue of them being a squatter if they do not leave the property.
You can call the police if they do not leave and state they are trespassing, as they are not on lease, nor are they room mates, but rather an employee (If you are paying them).
If they still refuse to leave, then they are attempting to Squat on the property.
As stated from the website of the attorney Danata Schner:
"In the U.S., a five-point test is typically applied to determine whether the right of adverse possession will be granted. The possession must be:
actual--the property must be actually put to use or occupied, in a way similar to the way nearby property is used by its owners
open and notorious--the use must be public and visible, not secret
hostile--without the permission or approval of the current landowner, for instance, without renting or leasing the land
exclusive--use of the property not shared with anyone else, particularly the current property owner
continuous--used continuously for a certain period of time, which may be 10 years, 12 years, 20 years, or some other period as determined by local law"
I do hope this is a hypothetical situation and not a concern regarding a current ongoing issue.