A useful setting for those who want a specific person within the organisation to approve/decline meeting room bookings manually.
Requirements: Office 365 admin role / Exchange Admin role in
Office 365
1. Go to the Microsoft 365 admin center (Microsoft 365 admin center - Home)
2. In the bottom left corner, click show all and then click on Exchange 
3. On the next page, click on “Resources” under recipients
4.Double click the room you want to configure a delegate for. Then, click on “booking delegates”
5. Under “Booking requests”, check the box “Select delegates who can accept or decline booking requests”, and then add a delegate by clicking on the +
6. Press save and repeat for any other room that you would like. Now all meeting requests for this room will first go to the delegate for approval.
Exchange
1. Go to the ECP (Exchange Control Panel). The URL depends on your organisation.
2. Click on “Resources” and then double click the room you want to configure.
3. Check the box “Select delegates who can accept or decline booking requests” and add a person 
You can also configure so that specific people do not need approval to book a room. You can read more about it here: Set scheduling permissions for a room mailbox: Exchange 2013 Help | Microsoft Docs
Good luck!