My question involves landlord-tenant law in the State of: Arizona

One of my roommates is moving out. There are 3 of us on the lease. He doesn't care who replaces him on the lease and doesn't care for our consent.

He said the landlord agreed to remove him and put a new person on the lease WITHOUT my other roommate or my consent.

Can they just amend the lease the like that?

This was rented to us as a group, not as a room for rent, that is why we don't want some stranger showing up to take the room.