Gordan mate, those spots on the roof still need some more sanding.

I've got the same thing on my roof of my car. There is still rust there & it'll come back soon if you don't get rid of it entirely.

unless you used a rust convertor on theose spots. even then, I've taken all the spots on my roof right back to bare metal. Better to be safe than have a rusty roof again in a few years!