(disclaimer: I'm Ruby on Rails developer)
I believe Ruby on Rails is pretty good to use as json backend.
You can easily found a lot of materials and screencast about integrating it with angular, like:
And building proper JSON api with Rails can be helpful for creating mobile app etc, there also very good material about crafting good Rails RESTful Api, f.e.:
- https://www.codeschool.com/courses/surviving-apis-with-rails
