Re: What's your recommended roof caulk/sealant?
If it's a rubber roof on your RV, there is a special sealant made for these. It comes in a standard size tube to fit into a caulking gun. DO NOT use anything but this product for rubber roofs - it is flexible and will stay that way for a long time (and it matches the rubber). I would think any RV dealer would stock this material.
EDIT: If the roof has previously been repaired by using silicone sealant, you should completely remove this first.
My class A is nine years old and the surface of the rubber sealant looked very bad, so I started by carefully scraping the old stuff off/out. When I got in a bit, I discovered that the sealant just below the surface was still pliable, soft and in good condition. Typically people use too much of the sealant, and it is often laid on in big gobs.