I\'m trying to figure out how to get rmagick on my app, and then make it work on Heroku?
It depends on which stack you are using on Heroku. The default Aspen stack includes a lot of gems preloaded. For compatibility reasons, the newer Bamboo stack has no preinstalled gems. It is always better to define your gem dependencies in the .gems manifest or in the new bundler style Gemfile.
More info:
Stacks: http://docs.heroku.com/stack
Gems: http://docs.heroku.com/gems