The lack of a rear ladder does not mean your roof is non walkable. For instance my old 2013 Cougar has a 3/8" OSB roof over the trusses. The reason a ladder was not installed is because there is a window on one side and that dumb BBQ rack on the other. At least that's what I was led to believe from a very reliable source at Keystone.
At 225# I have no trouble walking up there to inspect and clean.
Can't run or jump though.
