The type named in the heading of a relation would typically have to be defined partly in terms of a Semantic Role. In the Relation INVITES, for example, the person inviting belongs to the set INVITERS, which is a subset of AGENTS, i.e., the set of entities capable of acting volitionally. AGENTS is in turn is a subset of ACTORS. An entity belongs to ACTORS when, although not necessarily capable of volition, it “… in some intuitive way performs, effects, or controls the situation.” (I’ve lost track of the source.) In turn, the person invited belongs to the set INVITEES, which is a subset of PATIENTS, entities acted upon.
Agents, Actors, and Patients are all, of course, Semantic Roles.