To setup a recurring meeting on a conference room and have the rooms accept all those available timeslots and deny those that have a conflict (instead of denying all times);
Run both of these PowerShell commands for each room you want to modify:
Set-MailboxCalendarSettings -ID “RoomName” -ConflictPercentageAllowed 99
Set-MailboxCalendarSettings -ID “RoomName” -MaximumConflictInstances 20
You can change the percentage and allowed instances based on your own preference.
