I posted a question onto the Radio Userland discussion list. I asked why updates to my OPML blogroll don't automatically update my weblog menu. Nobody had an answer. A Google search came up empty too. But from my own checks it does seem that when you update your blogroll.opml file in your Gems folder, the ompl file itself upstreams automatically. However you have to manually push the updates to your menu - either by posting a new weblog entry or by playing around with the homepage templates (described below).