Jeffrey says stay with web pack.

gulpfile.js

@@ -13,5 +13,5 @@ var elixir = require('laravel-elixir');
 
 elixir(function(mix) {
     mix.sass('app.scss')
-       .rollup('app.js');
+       .webpack('app.js');
 });

package.json

@@ -8,6 +8,6 @@
     "bootstrap-sass": "3.3.6",
     "gulp": "^3.9.1",
     "laravel-elixir": "^6.0.0-9",
-    "laravel-elixir-rollup-official": "^1.0.4"
+    "laravel-elixir-webpack-official": "^1.0.2"
   }
 }