[Puppet Users] Right way to implement "roles" in hiera/puppet

I'm looking to implement a hiera backend for our Puppet installation, as we
routinely deploy systems that are of varying hardware, OS, and which may
have multiple roles they fill.

I've figured out, I think, how to handle the OS question through facter,
but implementing server roles isn't quite so clear. I want to maintain that
information on the server, not on the clients, but everything hiera-related
seems to use the facts for a given system. Installing a file containing the
roles on the client seems like a kludge. Is there a more hiera-ish,
puppet-ish way to accomplish this?

Thanks!