I'm ignorant , there i said it. The flash tool is good and dandy, but why not just use something like ROMtoolboxpro, for the recovery install. The previous answer is good though, you need drivers, but I must ask, if you didnt have the drivers installed correctly, then how did you root????
i would suggest CWM app for recovery install, but it crashes on me. Like I said Iam ignorant because I don't know your device,