Many RV roofs are not structurally designed for significant weight, such as a person. For maintenance, a thin sheet of plywood and a hands & knees stance is needed to spread the weight. Personally, I would not walk on a roof of a unit that does not have a permanent ladder. The ones that have a ladder are designed with extra support so that walking is not a problem. If you're not sure, a simple check with Jayco with your serial number will determine if it's OK to walk up there. JMHO
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.