If you get the Team Black Hat app (google it, is available on the web, not sure if it's still in the Market), and use it to download the 2.3.20 SBF zip file they offer, you can use Clockwork Recovery to flash that file to get your system back to stock Froyo 2.3.20 rather than using software to flash your phone from your computer.
Once you're on stock Froyo you'll have to find a Froyo root option that doesn't require a computer - not sure what's out there, frankly...you'd have to look around. If you can find a Droid-based root option, the remaining steps are all done from the device.