I just completed an install with the same motherboard (btw, awesome disto, LawlessPPC!). I must've re-installed 6-10 times for various reasons, and I'm pretty sure at one point I experienced the "Waiting for root device" message. I believe it happened only after a previous attempt, and I suspect it has to do with a pre-existing partition. What fixed it for me - if I recall correctly - was to delete all partitions on the drive (on another machine, running Windows), then try re-installing OS X.