According to the FAQs on the Second International RoShamBo Programming Competition page, this is the correct spelling for Eric Cartman's game where two opponents take turns kicking each other in the nuts as hard as they can.

This is distinct from Roshambo which is another name for the game rock, paper, scissors. The FAQs point out that taking turns, as in Roshambeau, rather than playing simultaneously affects the strategy. As the FAQs page states, "Going first tends to be somewhat advantageous in Roshambeau."

The page seems to have changed, but thanks to the magic of google the cached version is at if you're interested.