!!! You will be charged by-the-minute for Twilio's phone service !!!
Head over to Twilio and setup an account. Purchase a phone number and grab your auth token from the console.
It's easiest to use the gcloud tool to do this which is available here.
Run gcloud projects create PROJECT_NAME to create a new project.
First, make sure you have Go installed.
Then, go get github.com/thenrich/rooms. Modify src/github.com/thenrich/rooms/app.yaml, replacing YOUR_TWILIO_API_KEY with your Twilio auth token mentioned above and YOUR_APP_ENGINE_URL with https://[PROJECT_NAME].appspot.com.
Now, deploy the app to App Engine:
gcloud --project [PROJECT_NAME] beta app deploy
If gcloud complains about GOPATH dependencies, make sure rooms is in your GOPATH.
Go back to your Twilio console and add an incoming webhook to the phone number you purchased. The incoming webhook should be a GET request to https://[PROJECT_NAME].appspot.com/calls/incoming
Call your Twilio number and enter any conference ID when prompted. You should be forwarded to the conference room with wait music playing.