As soon as you click (right or left) on a rooms calendar that is in your Outlook but removed from Exchange some time previous, you may receive the error:
“The connection to Microsoft Exchange is Unavailable. Outlook must be online or connected to complete this action”.
Outlook is online but, again, the room has been removed Exchange 2007 some time previous.
ANSWER: Right click on any other calendar first and you will see the expected full list of options, including DELETE ROOM. Then right clicked on the room in question, and bingo, the full list of options appeared, including DELETE, which will function.