Most people use the cheap camel hair brushes. You can also get rollers made for epoxy. The dime store/box store rollers fall apart from epoxy from what I have heard.
Doing overhead is going to be rough to do. If anyway possible I would recommend flipping it over. With no experience doing over head it is going to lead to one massive mess on you and everything else.
If you go with epoxy rollers have a closed can with acetone in it. Drop the roller in it before the epoxy flashes. Close the lid. Just roll over a cloth and clean for next usage of roller.