def set_roles *roles
      roles = roles.to_symbols_uniq
      return clear! if roles.empty?
      set_ds_field bitmask.write(roles.to_symbols)
    end
def set_roles *roles
      roles = roles.to_symbols_uniq
      return clear! if roles.empty?
      set_ds_field bitmask.write(roles.to_symbols)
    end
saves the roles for the role subject in the data store
 see Troles::Marshaller::Bitmask
 @param [Array<Symbol>] roles list