Login to your admin account and go to Google Calendar.

Go to settings.
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Click on Add calendar.
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Click on Browse resources.
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Select and mark the room resource.
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Click on the room resource (Settings for other calendars).

Open the Share with specific people item.

Click on ADD PEOPLE.
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Enable your service account e.g. meetingroomapp@domain.com to Make changes to events for each room.
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