Many RT owners get a standard bike rack and put a hitch extension into the middle hitch receiver to hold the bike rack. This will put the bike rack out of the way of the Continental Spare Tire on the Roadtrek. Someone had found a bike rack with the extension already on it but I don't have a name or link for that.
You could also get a hitch carrier basket with an extension and attach it to the middle hitch the same way to carry anything.
The Roadtrek Cont. Spare is held in place with just a bar clip and it would not be a good idea to out very much weight on it as the support is made to drop flat down to start with.