It's not a huge tech challenge to patch or replace a section, using a roof tape like Eternabond, RV roof lap sealant, and/or new roof membrane. Even re-covering an entire roof isn't tough technically, though there is plenty of labor involved.
If only a small section is bad, you can glue down the edges of the tear and cover the gap with either self-leveling lap sealant (Dicor SW501 is almost the universal choice) or a rubber roof tape (Eternabond,DiSeal, etc). If a larger section, it's probably better to cut out the damaged section and glue down a new piece of membrane (EPDM or TPO) and seal the edges with lap sealant or tape.
If the roof membrane is getting toward end-of-life, say 20 years, it may be time to strip it all off and lay down new membrane. But if it's still sound, it can be coated with a liquid EPDM rubber that should give another 5-10 years of safe use. See roof coating products such as Liquid Roof, Kool Seal RV, or Henry's Tropi-Cool.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC