Hi Payroll TS,
In most cases, you don't need someone in charge of the room mailbox. Because Meeting Room will automatically accept or decline every room request. If you want to book Meeting Rooms in Outlook Calendar, you just need to choose Add Rooms under Scheduling Assistant tab when you create an event. Then you will be able to select the room you can book from the list.
And you can click Room Finder to perform more actions for the meeting you are going to create.
If you want to set an owner in charge of booking the rooms, then go to the Exchange admin center (https://outlook.office365.com/ecp/) and make that one be the delegate for meeting rooms. He/she will be responsible for accepting or declining requests that are sent to room mailboxes. No new calendar needs to be added.
Hope the above information helps. And if you still have more concern on this question, feel free to let us know.
Regards,
SD