Set-Mailbox "Croom-Main" -type room
Set-CalendarProcessing -Identity "Croom-Main" -AutomateProcessing:AutoAccept
Add-MailboxPermission -Identity "Croom-Main" -User mtraver@tagosgroup.com -AccessRights FullAccess
or Via UI just grant Domain users Full Access
Set-MailboxCalendarFolder -Identity Croom-Main@tagosgroup.com:\Calendar -DetailLevel FullDetails