You have to service the caulking for all of the roof penetrations every couple years. If your Roadtrek has the roof windows with the rubber frames around them those are a nightmare.
The servicing is basically pulling it all off from the roof vent, removing the screws, recaulking the screws, and recaulking the vent.
I like to use LePage Quad calking in Canada but I'm not sure what is available in the US.
It is nice and stretchy plus it adheres well. Do not use silicone as it's pretty much junk.
There is also RV specific sealants that you can pour over the vent seams but I've never used them.