Resources and Groups cannot be treated as staff members?

I have three options and I have the same issue with all of them:

1) a shared calendar

2) a room resource

3) a group

When I add any of them as staff to a group Bookings site, they are forced into the "Guest" role. This means their Outlook calendars cannot affect the Bookings availability. Is there a way to use these resources' calendars to block availability in Bookings? All resources have microsoft email addresses in our company.