?procedure for removing/preventing rust?

well i caught a large rock off my roof when i was on my way back from philly a couple weeks ago and i just noticed the “ding”(which is about the size of a pea) is beginning to rust a little bit.

1.) can i use rost off(spelled rost) to get rid of what little rust is there and then
2.)prime it without it spreading?

what should i do about this?

never removed rust before, cause it was never this small/doable b4

sand prime paint… if you want after you sand put some rust preventative primer/ rust converter in there