Roles missing in user list api

would like to ask, if somebody knows, why there are no roles within the user details in REST ADMIN API request. Roles are one of the most important user attribute so whats the reason they are not retrieved as other user attributes?Any suggestion? Thanks

GET /auth/admin/realms/{realm}/users 

  "id": "efa7e6c0-139f-44d8-baa8-10822ed2a9c1",
  "createdTimestamp": 1516707328588,
  "username": "testuser",
  "enabled": true,
  "totp": false,
  "emailVerified": false,
  "firstName": "Test",
  "lastName": "User",
  "email": "",
  "attributes": {"xxx": ["123456"]},
  "disableableCredentialTypes": ["password"],
  "requiredActions": []