I recently bought this car and it has rust spots on various places mostly the roof.

What steps should i take in removing the rust?

Thanks

 

The way I would handle it is to remove the rust through sanding or grinding the rust way with (~80 grit sand paper and a wire wheel), treating the spot with a phosphoric acid, then rinse (something like diluted Krud Kutter), to add a zinc coating to prevent further rust, and then coat with a 2k epoxy primer, build primer and paint.

Basicly, get the rust cleaned up and wipe with some phosphoric acid, rinse, and paint. Don't leave it with spray can primer (even the rustoleum sealer primer) that'll absorb water - and it'll start rusting again.