Here is what I was told when I called about my Work and Play toy hauler. If it has a metal roof, walk only in the middle, no support on the sides. (This is how a Work and Play is built). If it has a rubber roof, it has full wood to glue the rubber to, so an average person, under 200 pounds, will be fine. If two go up, as in to change an air conditioner, don't both stand in the same place.
As a part time tech, I have seen as many as 4 on a roof, when we had to change one of the rubber ones. All in different places, and none of weighed over 180 pounds.
Sorry, can't help with a Rockwood specfically, as we don't sell them.
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT