If you are still S-OFF from your previous root then you are in luck.
Check if you are S-OFF by booting into HBOOT - it will tell you right at the top.
If you are, download the latest Clockwork from here:
Recoveries | PvilleComp's
And follow the directions to flash it in HBOOT.
Once you have clockwork, ROM's and Mods HQ thread for a rooted Stock ROM and flash away, you'll have root back in no time.
If you are S-ON however this won't work and you'l have to downgrade to Froyo, re-rrot with Unreoked and then move on from there.
Hope this helps.