$onRootScope.js

var app = angular.module('YOUR_APP')
app.config(['$provide', function($provide) {
  $provide.decorator('$rootScope', ['$delegate', function($delegate) {

    Object.defineProperty($delegate.constructor.prototype, '$onRootScope', {
      value: function(name, listener){
        var unsubscribe = $delegate.$on(name, listener);
        this.$on('$destroy', unsubscribe);
      },
      enumerable: false
    });

    return $delegate;
  }]);
}]);