#1 - Call Keystone and ask their advise vs. a 'group of strangers' from the internet. Yes, a lot of years of advise, but the manufacturer would know best.
#2 - I don't have a ladder but I have gotten on my roof many times for maintenance and I am well over 220#
#3 - If/when on your roof, ensure you distribute your weight as much as possible, wear shoes that will not scuff/tear the roof material. When I get on mine I like to "crawl" more than walk and only stand up when I must. I clean my roof with a hose, bucket and scrub brushes on my hands and knees (I feel safer considering I am using soap and water which makes the roof slicker than normal).
Good luck and be safe...especially when getting DOWN from the roof.