When setting up a meeting in Outlook for Mac -- as opposed to setting an appointment -- organizers have the ability to add a Conference Room by using the Room Finder in Outlooks ribbon:
Clicking this pulls up the Room Finder interface, where organizers can choose a room from a list:
If one or more Conference Rooms have been set up as a Shared Resource by a domain administrator, they will be displayed and can be selected by the organizer. This, then, reserves that room for the organizer's meeting.
However, when creating a new meeting, or editing an existing meeting, there is also an "Add Room" option in the Rooms area of a meeting's schedule:
This acts similarly in that it can list a domain's conference rooms. However, selecting a room doesn't do anything. The Conference Room simply is NOT added to a meeting.
In our testing, we were able to confirm that this does NOT work in Microsoft Exchange either. Therefore, Microsoft must not have built that functionality into Outlook for Mac OR the EWS protocol doesn't support the "Add Room" functionality within Outlook for Mac. Regardless, this is not a SmarterMail issue, but entirely due to the limitations of Outlook for Mac.