I was going through the rtorrent wiki looking for what else I could do with rtorrent. I love the client, and I really hate it when someone says "$MyClient can do this, haven't seen rtorrent do it." One such feature was using rtorrent with RSS feeds that you get from torrent websites. There's this ticket which discusses this issue. As the ticket mentions, rssdler is an amazing utility which helps accomplish this. It took me a day to set it up to work with rtorrent, so I thought I'd share it with you folks and save you some time. rtorrent now watches a directory, which is also the destination folder that rssdler downloads torrent files to.
I'm going to submit the rssdler package for review soon. For the time being, you can install it locally in ~/bin and use it. I've placed the .rtorrent.rc and ./rssdler/config.txt files to my fedorapeople space that you can download and easily customize.
Here are some additional docs that you can read up: