Caulking

Yes. Get a plastic scraper and some Dicor lap seal and go at it

Watch this short video: Prevent RV Roof Leaks (Dicor Maintenance)

Caulking is the process of applying caulk.

I've been a boater all my life, and wonder why Sikaflex is not commonly used for RV's? (or is it, perhaps using a different name?)

I found this product works great for many years, without breaking down at all. I have some areas it was used on my boat 18 years ago, and it still looks like it's newly applied. No cracks, peeling, and still remains flexible. UV doesn't seem to affect it like silicone and other caulks I've used for things.

FYI, in general, stay away from silicone caulk. Nothing will stick once you apply it not even more silicone.

Can I jump in here and ask this question? Can you also use Dicor Lap seal in other areas, beside the roof? I will be removing the rear camera, and will need to caulk around the hole where the wires going into the hole. I will also need to caulk around some running lights on the wall, near the top. fyi. These areas are mentioned are on painted surfaces of the fiberglass wall.

Dicor makes 2 kinds of sealant- self leveling and non-self leveling.

Use the self leveling for horizontal areas like the roof. This sealant will "spread out" after being applied.

Use the non-self leveling for use in vertical situations (like your wire entry).

Ditto on what Hondo says.

Jose