how can i restrict access for particular MountableEngine inside my rails application in routes

Question

i want to grant access to /samurai (mountable engine) only for users that have admin as role:

how can i do that?

my routes

authenticate do
   mount Resque::Server.new, :at => "/resque"
   mount Samurai::Engine => "/samurai"



 scope "/admin" do
  resources :customers, :images,:categories, :groups,:redirects, :projects, :specs, :indices,:glossaries, :invoices, :users, :products

  resources :comments do
    member do
      post 'approve'
      post 'moderate'
      post 'disapprove'
    end
  end
end

P.S = im using CanCan and Devise

---

Updated

i'm really new in Ruby, i've solved my problem this way!

1) creating a file at config/initializers;

2) in that file i 've put that code below;

Samurai::ApplicationController.class_eval do
  before_filter :restrict_access

  private

  def restrict_access
    user = current_user
    head :unauthorized unless user.role_id == 1
  end

end

how bad its that?