Yes you can. Visit the 1st link in my sig, post 13. If you have install issues then visit the 3rd link in my signature. Basically:
download the drivers and rsd lite, install both.
download sprecovery sbf file and flash it with rsd lite
flash any rom you'd like to, with sprecovery
you should now have a functioning phone again.
From there make a backup.
Then flash other roms if you'd like, and reinstall rom manager if you'd like.
Personally I just use sprecovery and follow whichever rom installation instructions exist for the rom I want. In most cases you just rename the rom to update.zip on the root of your card and install it.