On the main page you scroll down all the way to the bottom and on the left under the "meta" header there is an option to register and log in. Good luck.
If you want the latest news on PR I would sign up for Fireshadow's forums they are much cleaner and does not have as much spam, the web address is: "
http://projectrooster.b1.jcink.com/index.php" These forums have the latest PR news including info on the upcoming server.