At the bottom of this page, there's a “Try it!” section. You need to turn the “Authorize requests using OAuth 2.0” on and sign in with your room account/email that has subscribed to the room resource in the pop up dialog.
Click the big blue “Execute” button, and you will see response in JSON format. Now you can press “Ctrl+F (command+F in Mac OS X)” and search for your room name.
You should see your room name in the "summary" response since you've already subscribed the room resource .
Note: Google Apps management portal has bug if you have previously edited the resource name. If you cannot find the current resource name, please find the originally created resource name.