Hey mate, I've done around 80k kms travelling oz in my Landcruiser and VT wagon mostly in outback sa and the top end. I've hit one roo and it had to be in the VT, was still drivable though.
I've always tried to limit exposure by not driving at dawn and dusk, up around that way I've found the chance of hitting cattle more likely than roos due to them congregating on the roads at times.
Whereabouts are you planning on heading?