Sorry, I missed the part that it was a fiberglass roof. I would think that you would use the same cleaners etc that you use on fiberglass boats or cars (Corvette).
Richard & Jill
2014 Flagstaff 832IKBS Classic Super Lite
2018 Silverado 1500 Crew Cab Z71 4WD All Star Edition
Camping since 1989, Seasonal since 2000.
Car Shredder Op/Tech, Scrap Metal Recycling - retired