Using a virtual RubyGems repository you can aggregate both your local and remote repositories.
You need to set the right repository source URL, in the same way as described in Usage for a local RubyGems repository, just with the appropriate repository key as follows:
source: http://localhost:8081/artifactory/api/gems/<repository key>/
target: http:// localhost:8081/artifactory/api/gems/<repository key> ( no slash at the end!)