Yakima or Thule makes a ratcheting boat lift/rack called a "Hullivator" that can put a boat up on a tall vehicle - but I'm not sure if that would work with all the "stuff" that tends to be on the roof of an RV.
In the past, I owned a Sea Eagle "FastTrak 385" which is a really tough inflatable with relatively low sides and a skeg. It's rated to Class III whitewater, and be paddled solo or tandem; I paddled mine mostly on inland lakes. It's pokier than a hard sided boat; but tracked well. Packs up to the size of a large duffel bag.
If I wanted to bring one of my boats along on my travels, I would probably opt for a trailer that would also carry bikes and maybe offer storage for other things. Maybe a small enclosed trailer with a boat rack on top?
Ed, Deb, and 2 dogs
Looking for a small Class C!