Connect-ExchangeOnline
$resource = "ResourceMailboxUPN@yourdomain.com";
Get-Mailbox -RecipientTypeDetails RoomMailbox -Identity $resource | Set-CalendarProcessing -AddOrganizerToSubject $false -DeleteSubject $false -DeleteComments $false -RemovePrivateProperty $false
Get-Mailbox -RecipientTypeDetails RoomMailbox -Identity $resource | Get-CalendarProcessing | fl