First of all, according to this answer, the :cache => true option on stylesheet_link_tag and javascript_include_tag doesn\'t work o
:cache => true
stylesheet_link_tag
javascript_include_tag
GitHub has a good answer for this, and I'm sure you could modify Heroku's deployment scripts to integrate:
http://github.com/blog/551-optimizing-asset-bundling-and-serving-with-rails