Roommate/Lease Agreement

My girlfriend and I just recently bought a house and will be paying mortgage payments starting in February. We had planned on having a couple of my close friends stay with us and of course pay for staying there. We had previously talked about a lease agreement but now they are saying that they want to bring up a roommate agreement because they want to be our roommates not our tenants. Is this even possible or necessary for us to do this since we are the rightful owners of the home? My girlfriend and I's name our the only names on the mortgage and we paid the earnest money/deposit for the house and plus did most of the fixing up of the house. I have looked over some roommate agreements and they all include the term landlord. Aren't we the landlords/owner of the property? Please help!

They will be tenants; they should not have any problem with that.