Office 365 - Outlook shows Global Address List clicking "Rooms" during a meeting request

I just recently discovered Room List Distribution Groups, which provide a much more functional method for reserving rooms using the Outlook Room Finder.

Have you tried using this, and seeing if it also resolves the problem you are having with selecting the wrong address book?

To set up a room list for all room mailboxes on your site, you use the Powershell commands

New-DistributionGroup "Conference Rooms" -RoomList 
Get-Mailbox | Where-Object {$_.RecipientTypeDetails -eq "RoomMailbox"} | %{add-distributiongroupmember -identity "Conference Rooms" -member $_.alias}

Once you've set up a room list, it is visible in Outlook when making a new Meeting request. The nice feature of this is that it will only display the available rooms for the date/time of the meeting.

This is the resource I used for accomplishing it with Office 365, but the Powershell commands and end-user experience are the same in on-premises at least back to Exchange 2010.