code: public ImmutableList<RoleInfo> getRoles() {
          TypeReference<List<RoleInfo>> typeReference = new TypeReference<List<RoleInfo>>() { };
          
          String errorMessage = String.format("Failed to retrieve roles from Conqueso server: %s",
                  conquesoUrl.toExternalForm());
          
          return ImmutableList.copyOf(readObjectFromJson(typeReference, "/api/roles", errorMessage));
      }
docs: Retrieve information about the roles from the Conqueso Server.
  @return the role information
  @throws ConquesoCommunicationException if there's an error communicating with the Conqueso Server.