I actually paid a mobile RV repair to reeal the roof, I don't think they removed the old sealant. they resealed all seams and around all edges and vents/ac/etc. They also cleaned with a cleaner and brooms first and applied a conditioner when they were done. They charged me 200 hundred dollars and come to my house to do it, very reasonable. They used Dicor sealant I think just like from the factory.
Dan, Kelly and Maddy.
Cupid and Kandi the Camp Dogs
2006 Salem LE2013 Ford F150 Ecoboost Supercrew w/ factory tow package