There are circumstances where a crawlspace doesn't have to be insulated, but if there are no outside vents to vent the space then you basically have to insulate it. I don't know what you mean by foam bricks, but I have my doubts that you'll get the minimum R value requirement without insulating the wall cavities.
No idea what you mean by open rafter joists.
Can you post a picture or describe further? Rafters and joists are not the same thing, and there are situations where either would need insulation. Joists are the floor or ceiling, rafters are the roof.