Single entry point for many scopes in Devise.

application_controller.rb

class ApplicationController < ActionController::Base
  ...

  private

  def after_sign_in_path_for(resource)
    if current_administrator && current_administrator.is_admin?
      [:admin, :admins]
    else
      root_path
    end
  end

  def after_sign_out_path_for(resource)
    case resource
      when :administrator
        [:new, :administrator, :session]
      else
        root_path
    end
  end
end

base_controller.rb

class Admin::BaseController < ApplicationController
  respond_to :html, :json, :xml
  before_filter :authenticate_admin!

  private

  def authenticate_admin!
    authenticate_administrator!
    unless current_administrator && current_administrator.is_admin?
      respond_with current_administrator, location: after_sign_out_path_for(:administrator)
    end
  end
end

routes.rb

Myapp::Application.routes.draw do
  devise_for :administrators

  namespace :admin do
    resources :admins
  end
end