Best way to treat the rust on my roof?

^^^@Oldmanmopar That is the ultimate method IF you have a guy that can Do it! Worping metal is easy , be careful.
Second best. You have pitted metal I bet. It can be DA, use a big wire CUP on a right angle grinder, but that does not take care of pitted metal with rust in that pit. I use a phosphoric acid solution to attack that. There are many hundreds of threads here on that. I personally, have not used a "rust convertor" type product in 40 odd years, every since every body man I had talked to said don't. Never needed it.
Like said above^^^ after the metal is clean, using a top grade epoxy primer is keep, 3 coats! Then TOPCOAT.