I’m having the same problem, and the codex page wasn’t much help.
To join a blogging ring, I need their blogroll somewhere on my site. Since it’s an incredibly long blogroll, I want to give it its own page as other members have. (It’s the powered by blogrolling kind, if that helps.)
I turned off the rich text editor, thinking I could just paste in the code, but even when I have the “use the rich test editor as the default” unchecked, um, I still have the rich text editor showing, hence no way to paste in the code.