Force SSL exception for Rails app

Question

I'm working on a specific case where I want to force SSL in a Rails app, I've tried using:

Rails.application.configure do
    config.force_ssl = true
end

However, there are a couple of endpoints that load content from 3rd party websites using iframes and I'm getting a Content-Mixed error because some of them don't support HTTPS.

Is there a way to mark certain routes as exempt to the force_ssl config in Rails?

Working on a Rails 4.1.x app, thanks!