According to the Bantam Flier, Rocky Mountain Edition brochure printed in 2004:
It is constructed with a "welded aluminum framed roof & sidewalls, laminated with 1" block foam insulation (R-5)."
As an RV Inspector, I have had the opportunity to climb atop quite a few RV's. The aluminum frame should hold a reasonable amount of weight. From my experiences, if the framing ribs are the slightest but visible, only step/kneel on the ribs. If the rubber roof (which your's has) is dried/cracking, you may do further damage by walking/kneeling on it. A 4' x 4' piece of plywood may be useful, but watch the corners.
My rule of thumb is to err on the side of safety and caution. If it is bad, let a certified maintenance tech inspect the seals and recommend roof repairs. For the cleaning: If the rubber is suspect - clean from the ladder; only use the recommended cleaning product for rubber roofs and use a soft brush - a hard brush may get it cleaner faster, but can also damage the rubber.
Good Luck, Safe Travels & Happy Camping