Recently (actually last week), we released a new version of rollbar.js that has a few fixes to play nicely with Browserify and Webpack. It's being served from our CDN and the source is on GitHub.
We've also put together examples showing how to use rollbar.js with each. If you use Browserify or Webpack and want to include rollbar.js that way instead of using our standard snippet, this is your lucky day:
Thanks to @altano for helping with this.