that's what you get for playing around with root huh?
you've not bothered to provide information about what distribution you are using so we can't help you that specifically, but try to reinstall all the X packagesl again, probably by forcing, if you can't get it going you'll need to reinstall linux completely really which is probably what you'll end up doing as there aer so so many pakcages that you would have affected by doing that.
hot tip - don't do that again!