The docs say that's not the case, but that's not really accurate as the root role can already access system.indexes and system.namespaces so we should probably remove this line:
root does not include any access to collections that begin with the system. prefix.
and possible amend the next paragraph:
For example, without the ability to insert data directly into the:data:system.users <admin.system.users> and system.roles collections in the admin database. root is not suitable for writing or restoring data that have these collections (e.g. with mongorestore.) To perform these kinds of restore operations, provision users with the restore role.