Most of it is the packaged stuff, but Eco Meats at Belconnen Markets has possum, roo, wallaby, croc, and a whole range of other interesting things.
Apparently the supermarket in Yass has bulk side of roo, but I haven't gone there myself to check it out - yet.
I also haven't yet been game (heh) to use roadkill. Possibly because we've been lucky and haven't actually hit anything yet. If I hit it, and it wasn't in bits everywhere, I would consider taking it off the road (for safety, you know).
Note that in some (all?) states, collecting native roadkill isn't exactly legal, I don't think. So naturally the opinions in this thread are only those of the author etc and so on.
We have roos on our property and one of these days we're going to get in a shooter for "culling" purposes, and I'll learn how to correctly butcher meat ...