a girl who is butt ugly and a slut but who always tries to jump into bed with the nearest person she see's hence the "roo" like a kangaroo, that jumps all over the place. a rooskank tries to jump into having sex with you. she is a slut. a rooskank will try to force herself onto someone, normally they are not fine.
Rupert: Damn, that girl is a Rooskank !
Clive: yeah i know she is so damn ugly! she tried to jump into bed with me, practically forced herself one me!
Rupert: what? what a slut, she tried it on with me as well.
Clive: if im really desperate i'll have the Rooskank !