Roles are intended to be aggregator Puppet classes. Apply a single role at the classification level. If more than one role is being applied to a single node, perhaps it should be a profile instead, or perhaps that combination of profiles should be turned into a role.
This is the role module for the Puppet Labs SE Team. It is a site-specific module, and is not designed to plug-n-play into other environments. In some ways, this is one of a few modules that define the environment.