code: def role_list(request, filters=None):
      
      manager = keystoneclient(request, admin=True).roles
      roles = []
      kwargs = {}
      if filters is not None:
          kwargs.update(filters)
      if 'id' in kwargs:
          try:
              roles = [manager.get(kwargs['id'])]
          except keystone_exceptions.NotFound:
              roles = []
          except Exception:
              exceptions.handle(request)
      else:
          roles = manager.list(**kwargs)
      return roles
docs: Returns a global list of available roles.