Now that our rig is in hibernation, I am going through my list of things found when cleaning up the rig at the end of this season. Many things are applicable to everyone, this one in particular can get serious if ignored.
On our roof (and yours too) every vent is sealed to the fiberglass roof at the factory using what looks like a thick white poured liquid the consistency of molasses. That soft white rubbery material on our roof is now eight years old but has seen much less than one year's worth of sun exposure. Our rubber is still very soft and pliable, but is splitting apart in very small amounts around the perimeter at the edges of the Fantastic fan, bathroom fan, and bathroom skylight. It is not significant but it is there. I do not see any water stains on the inside ceiling anywhere so maybe there is more of the same goop between roof and flanges, preventing the water from getting inside.
I bought a squeeze tube of white outdoor use 100% silicone caulk and touched up the areas in question.
I know most of you store your rigs outdoors, always exposed to the elements. Maybe you with older and even newer rigs have the same issue developing as us. I recommend you get up on your roof and closely inspect that white poured sealant for any separation or cracking, and seal up anything questionable.....especially before winter sets in.
I hope you share what you find here for others to read about the severity or lack there of.