Any experience with the product, "Through The Roof"

The manufacturer makes no suggestion that it is a silicone product. It should work well on your fiberglass roof.

Thanks to everyone for the info! I was planning to use Eternabond tape over it. Did not know that Through The Roof was silicone. Eternabond does not adhere to silicone.

I have used it on a galvanized building roof to seal around a problem flashing. It worked well. It's silicone, but very high quality, made for that purpose. I would probably not use it on a rubber or TPO roof though. Dicor Lap Sealant is the way to go IMO. Or Eterna-Bond tape, depending on the scenario.

I think your better off using a product that is formulated by the roofing manufacturer (assuming TPO or EPDM roof). Other products make work for a while and then let go when you don't expect it.

From the Manufactures site:
Can I use Through the Roof on my camper/RV?
Through the Roof is highly recommended for most surfaces on RV's/ Campers. It can be used on rubber roof membranes; however, while it will adhere as usual to the rubber membrane, it may ripple or warp the rubber membranes over time. Cosmetically, it does not look good, but the performance of the Through the Roof remains the same.

In addition, some RV's / Campers use polyethylene and polypropylene materials. Through the Roof will not stick to them, so keep your eye out.