Your contractor should be licensed by the city you live in or the state, specifically, Oklahoma. Don’t work with a contractor who isn’t licensed. A good contractor will be able to present a copy of their license when asked. This can cover any liability the roofer could incur and ensures that you don’t have to burden that liability. There are those out there that will do your roof for cheap out of the back of their pickup, but it isn’t as safe as hiring a licensed professional.