Motorhome and RV roofs are predominantly single-ply commercial roof systems. They are also notoriously problematic. It is important to inspect your roof regularly. Look for any damage, check around all of your penetrations for broken seals, also check along the edge of the system for any defects. Typically, an RV dealership can charge anywhere from $8,000 to $15,000 for a roof replacement. It is also important when buying a new RV to ask what the warranty is for all of the different systems of your vehicle. Many manufacturers only warrant the structure for 1 to 3 years. If you are uncomfortable with inspecting your roof system, I suggest you contact a local commercial roofing contractor for an inspection. Most reputable roofing companies will usually offer this service for free or at a reasonable cost. Ask what is included in their inspection and report. Regular maintenance will save money in the long run and also extend the life of your roof.
The good news is if you do need a new roof, there are options available at a fraction of the cost offered by an RV dealership. It is important to explore your options and to ask for references from companies you are dealing with.