A coat of wax or protectant will help keep the dirt & debris from sticking to and possibly staining the roof, just as it does on the body of the vehicle. Makes cleaning faster the next time.
When washing or waxing, I always start at the front and move towards the back, so that I am never standing on a wet or slippery surface. Just like any work at heights you have to respect gravity and always be aware of your situation.
And, as they say in the roofing business, "Never step back to admire your work"
2008 Itasca Meridian 37H & 2015 Flagstaff T12RBST
2011 & 2012 Len & Pat's "One lap of America"
27K miles & 41 states in 13 months - Woo Woo
Yellowstone Lake 6-1-2012