First fact:

At the beginning of 2002 there were 63 million of them, the most ever recorded (estimated) and the most that have ever existed ie there are wells, bores, tanks, drains, and dams of water where it used to be dry for 11 months of the year. The roos have benefited from this.

The drought of 2002 did knock them about a lot but like much Australian fauna they recover their populations in a season or two.