I'm giving my roommate that is not on the lease 35 days notice written by me .I want him to sing to letter saying he will be gone by then but he might not sing it . In that csse what should I do?

You evict him according to the law in your State/Country.

He doesn't have to or need to sign. You just need to show that you gave him the notice. If he doesn't leave by the deadline, you go to court for an eviction order.