[JRTJH]

I suppose the most "sage advice" is contained in the Keystone Owner's Manual, on page 87 in a WARNING: "Only RVs with factory installed ladders have walkable roofs."

That said, many members who do access their roof use either plywood squares covered with carpet or 2" "pink foam" squares to use as stepping stones that span the roof rafters. Remember, your roof decking is probably 1/4" OSB sheeting and probably on 24" centers. That isn't a lot of structural strength, so walking on it may well cause an unwanted hole, especially if, as you say, " I'm not exactly skinny..."

As for the weight limit, most people under around 200 lbs haven't reported issues using "pads" to access their roof. However, if you're over that, then you might consider some "sage advice" and just use your ladder with some foam noodles to pad the ladder where it touches the trailer sidewall and do you're inspections and maintenance "from the safety of the ladder".....

Here's a photo of the ladder that many of us have found to be easy to load, sturdy, light weight and the foam noodles fit well.....