Only half the roof is this way the other side is fine where its not shaded. I plan on selling my house next year so paying for a new roof is out of the question. My metal sheds only lasted 18 years and are totally rusted now. I live in the Pacific Northwest with a roof that is not pitched correctly for a metal roof at all.
While it won't help an already damaged roof, , a broad copper ridgecap (that is raw copper with no sealants!) helps inhibit moss growth, Ditto for galvanized.....
For some reason many jurisdictions have outlawed these proven solutions and perhaps there will be unfortunate consequences in flower borders, a horticulturist might have answers.
Nothing is foolproof to a sufficiently patient fool!
I hate people who use big words just to make themselves look perspicacious.