The joke is in reference to a Ouija Board, which is a game where people would hold onto a pointer (planchette) and "supposedly" let spirits guide their hands to a series of letters/numbers spelling out words/phrases. Essentially it is a game where you pretend to commune with spirits. A Roomba is a small robot vacuum that on its own moves about the floor and vacuums the room without someone needing to guide it. So in the meme, the joke is that the Roomba would move over the Ouija board on the floor, commune with the spiritual world and inadvertently summon the devil.