To get a relationship type object from the repository, use RAMSession.getAllRelationshipTypes() or RAMSession.getRelationshipType(String name).
//Fetch all relationship types
RAMRelationshipType[] relationshipTypes = session.getAllRelationshipTypes();
//Fetch a relationship type by name
RAMRelationshipType relationshipType = session.getRelationshipType("myRelType");
//Fetch a relationship type by Display Name
relationshipType = session.getRelationshipType("My Relationship Type");