How I made I18n_routing working with Devise. Couldn't translate routing scopes in any way, so I added a little workaround to the gem and...

I18n_routing_common.rb

# I18n_routing/lib/I18n_routing_common.rb

  # Return the correct translation for given values
  def self.translation_for(name, type = :resources, option = nil)
    # First, if an option is given, try to get the translation in the routes scope
    if option
      default = "{option}Noi18nRoutingTranslation"
      t = I18n.t(option, :scope => "routes.#{name}.#{type}", :default => default)
      return (t == default ? nil : t)
    else
      default = "{name}Noi18nRoutingTranslation"

      # Try to get the translation in routes namescope first      
      t = I18n.t(:as, :scope => "routes.#{name}", :default => default)

      t = I18n.t(name.to_s, :scope => type, :default => default)
      return t if t and t != default
      
      # this is what I added
      t = I18n.t(name.to_s.gsub('/', '_'), :scope => type, :default => default)
      return (t == default ? nil : t)
            
    end
  end

locales.yml

# config/en.yml
en:
  named_routes_path:
    users_new_registration: "users/registration"
    users_edit_registration: "users/registration/edit"
# config/it.yml
it:
  named_routes_path:
    users_new_registration: "utenti/registrazione"
    users_edit_registration: "utenti/registrazione/modifica"

routes.rb

# just an example, these are not all the routes needed :-)

devise_for :users, :skip => [:sessions, :registrations] do
  get "users/new_registration" => "users/registrations#new", :as => "user_registration"
  get "users/edit_registration" => "users/registrations#edit", :as => "edit_user_registration"
end

You could pack it as a pull request to the gem! That would be awesome :)

PLease pack it as a pull request:)