ErrorItemNotFound when trying to retrieve room calendar via MS Graph API

I've tried all possible ways, but there is no way to get access. This is what I've tried out the following in the Graph explorer:

• https://graph.microsoft.com/v1.0/users/[email protected]/events -> DelegatedCalendarAccessDenied
• https://graph.microsoft.com/v1.0/users/[email protected]/calendarView?startDateTime=2019-01-14&endDateTime=2019-01-18 -> ErrorItemNotFound
• https://graph.microsoft.com/v1.0/users/[email protected]/calendar/calendarView?startDateTime=2019-01-14&endDateTime=2019-01-18 -> ErrorItemNotFound

All three on both the v1.0 and the beta.

It isn't an issue with rights, because for my testing I granted the Graph Explorer the Directory.ReadWrite.All scope. Resulting in the following scp claim.

The first requests seems the most promising (because of the different error), I also made myself a delegate with full control of the rooms-mailbox. That still didn't help.

A request to https://graph.microsoft.com/v1.0/users/[email protected] gives a result, as in a result describing the meetingroom.

{
    "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#users/$entity",
    "businessPhones": [],
    "displayName": "Meeting room 1",
    "givenName": null,
    "jobTitle": null,
    "mail": "[email protected]",
    "mobilePhone": null,
    "officeLocation": null,
    "preferredLanguage": null,
    "surname": null,
    "userPrincipalName": "[email protected]",
    "id": "3e0a7b7e-xxxx-xxxx-xxxx-xxxxcxxxx120"
}

After doing all these tests, I can only conclude that you cannot access the events in a rooms mailbox. This is either intended (as in only use the scheduling assistant) or a bug.

Maybe some of the Microsoft guys around here could clarify this?