Ember - Loading Nested Route in parent route

I have two routes:

• /users/:user_id (aka user)
• /users/:user_id/roles (aka user roles)

I now want to show the user roles within the user route. I still want to have a separate user roles route.

When user roles are being loaded within the user route, the page should show the user roles section/template as loading (Because of requests to the server for user_roles).

How do I achieve this?