if you're already running 2.1, you need to flash back to 2.0.1. follow the instructions here.
http://androidforums.com/all-things-root-droid/47349-now-you-can-live-without-fear-bricking.html
i just rooted a few minutes ago and was trying to figure out the best way, this was the easiest and only took me like 20mins. also, get clockwordmod from the marketplace - the paid version. once you've rooted, you can use the app to download and install roms. quite easy.
if you know more than me about what you're doing, feel free to go about another method. this just happened to be extremely easy.