Aussie slang for Red Rooster, a fast food chain similar to KFC (aka Kolonel's Fucking Crap). Generally less popular than KFC due to their use of shitty crumbed chicken in their burgers, and the fact that they build new stores with a single cashier.
The fun stems from the use of the word root in Australia as slang for sex. This provides an endless source of amusement to us when we hear about Americans 'rooting' for their favourite sports team.
I'm going down to Red Rooter - want anything?
one who fucks a chick when she has her rags
why is your dick red? are you a red rooter?