Hello and welcome to Android Forums.
I check to see if devices are rooted by downloading Root Explorer (or other apps requiring root privileges to run, many are free) from Market, then attempting to grant the app "su" ("superuser") status.
If that succeeds, the phone is rooted.
Another way is simply to use a terminal emulator and type in "su." Again, if that succeeds it's obvious you have a rooted device.
There are many ways, those are the ways I do it.
I put your question in the Droid forum for you.
Take care, have fun.