Cool, I must have missed that. It would be nice, then, if you could also have a node be tagged with multiple roles (as well as add/remove them in a way that propagates).
Dynamic roles is a fairly hard problem, which we hope to solve by building a different tool on top of Serf in the near future. If you want multiple roles that are static, it can be simulated by just providing a comma separated value as the role (since that is just an opaque string value to Serf)