Dumb painting question

[Locke N Load]

They say there are no dumb questions so here goes. I will be rolling primer and paint in three separate areas; bottom, sides, everywhere else. 3-4 coats each of primer and paint means a total of 20 applications. Some big flat surfaces and some small nooks and crannies so I figure 9" and 3" roller covers. Paint for the bottom is Interlux VC Performanc Epoxy and the sides and rest of the top will be Alexseal.

Do I need to buy 20 covers of each size or can they be cleaned between coats and reused? One for each primer and one for each color/type of paint so 3 and 3? I am guessing they cannot be cleaned and I need to buy 40 covers, but figured I could ask before buying all that if it would be a waste.