Speak with them and explain to them why you are needing them to move within 30 days.

If you don't want anger/confrontation/whatever issues, then just let them know you have issues or are in need of space or whatever. In other words, take on the 'fault' of this situation not working out without blaming them.

Since they are not on the lease, they have no recourse.

As an aside, are you permitted (in your lease) to rent out rooms? If not, blame it on the lease and the owner wanting this situation to cease.