Are there any regulations for picking up roadkill in Australia?

I am planning on going to Australia next summer with some friends, I am a skull collector and I would like to get some animals that are not in the U.S. I do not poach, I only pick up animals that died of natural causes, have been hit by cars, or humanely euthanized, then I clear them of any flesh and then soak them in hydrogen peroxide and/or bleach. Is it legal to do this in Australia? what are the laws? Please I need detailed answers.... and most of all, how could I bring them back to the states? Something tells me it would be difficult explaining a suitcase filled with skulls to a security guard at an airport. =P