Alt-rooted means that something other than the priced name system is in force.
As used here it means peering with the name servers here, which is automated like in letsencrypt as part of the SSO/user provisioning setup.
The easiest way to do this this is add the following servers, which are non-recursive, to the top of your resolver config such as resolv.conf:
or their ip addresses if your resolver requires that.
- see en:Alt root