It says "still waiting for root device", root device is the partition where OS X installed, and it cant be found to load OS X.
The problem is you are missing some kext to add support for the storage controller that handles the hard disk where you installed OS X.
Solution would be finding out what storage controller you are using and adding the right kext.
Assuming you are using P45's main SATA ports, that means storage controller is Intel ICH10. That is supported out of the box with no additional kexts if running in AHCI mode, if its running in IDE mode you would need a modded AppleIntelPIIXATA.kext with support for your device id.