You could ask on the Rose mailing list, but my general advice is to avoid putting objects in your session. You should keep session data as small as possible because it gets sent to and from your database and passed through Storable on every hit. If you just save a unique ID instead, it will be much smaller.
Agreed. It's info needed on each request, but I think I can drop my new found obsession with Rose DB here and just store the needed info in a hashref in the session.