Role permissions to read `.monitoring-*` indices?

I want to read the .monitoring-* indices (provided by x-pack) within Grafana.

What privileges do I need to grant the grafana user role? I have tried creating a role that allows read and read_cross_cluster to the index pattern .monitoring-*. It comes back with the error:

No date field named timestamp found

If I use an admin user, however, the data source test succeeds in Grafana and it can read the index just fine. This is why I think the issue is with role permissions.

The answer is read and view_index_metadata.