Para obter um objeto de tipo de relacionamento do repositório, utilize RAMSession.getAllRelationshipTypes() ou 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");