List routes without devise filters

I've just noticed that an action didn't have a before_filter of any kind, which resulted in the request erroring on current_user.is_admin? in view code. As an anonymous user shouldn't be on this page, I concluded the problem was that there wasn't a before_filter :authorise_user, and I want to check if there's any other actions or routes that lack such a filter, apart from logging into the system.

How can I list all routes or actions that don't have a devise-related filter on them?

I'm using Rails 3.2 and Devise 3.