you mean 'rooting for,' or is 'rooting' a euphemism like 'plowing'?
given that the show would still be "believable" if they were all "rooting for" each other,
i'm guessing "rooting each other" is being used euphemistically to mean, as ockraz suggested,
"plowing" 🙂
in any case, this is still one of my top five favourite shows!