The most important thing to do is check the manufacturers specs in terms whether it is a "walk on" roof and, if possible, any weight limitations. If you were concerned about it, you can use a plank or piece of plywood to distribute the weight over two or more trusses.
I'm going to have a ladder installed on my trailer in a couple of weeks, but I would rather do as much cleaning or work from a ladder placed alongside the trailer rather than walking on the roof....I'm not getting any younger and I don't want to take a tumble!