If you have GSuite, E2H will read your Calendar Resources and Calendar Buildings list as the list of rooms/buildings that E2H will see.
Starting in v1.6.3, you can also choose an option to include personal calendars as room calendars in addition to room resources. This will allow you to control other types of rooms using shared external calendars as room calendars.
You can also include additional metadata for E2H in the description of the room resource, such as:
•{bldgname:xxxxx} = Associate room with given building name
•{exclude:true} = exclude the room from the room list in E2H
•{capacity:50} = defines the maximum capacity of the room (50 people in this example). This is used to determine %capacity by Events2HVAC.
Note: The room metadata will take precedence over the Resource.Capacity and Building.Name to preserve legacy room lists. You will need to remove the metadata to retrieve the Resource/Building properties.
Google Help: https://support.google.com/a/answer/1033925?hl=en