Maybe, maybe not. Every roof is built differently. I'm 195lb and feel very comfortable on most RV roofs. Solid. But there are some others that I just won't go on unless I'm on all fours, too much flex for me.
My friend who is 260lb does his own fifth wheel roof, but he is always on all fours.
Since you are asking, you are evidently concerned. Perhaps it would be worthwhile to hire the work out and then you can inspect it from a ladder on the edge?
Scott and Liz - Southern NM
2012 Wildcat Sterling 32RL - w/level up (best option ever)
2007 Chevy 2500HD 4dr short bed Duramax w/allison
Reese Fifth Airborne air ride king pin coupler with Sidewinder