Tem que validar no controler da aplicacao e no de admin ... isso nao é o melhor jeito, mas funfa beleza

application_controller.rb

#!/bin/env ruby
# encoding: utf-8
class ApplicationController < ActionController::Base
  protect_from_forgery
  def after_sign_in_path_for(resource)
    inicio_path
  end  
  def after_sign_out_path_for(resource)
    inicio_path
  end  
  
  def set_admin_locale
    I18n.locale = :"pt-BR"
  end     
  
  def current_ability
    @current_ability ||= Ability.new(current_user)
  end
    
  def authenticate_admin_access!
    if !current_user.nil?
      Rails.logger.info "####################################################################################"
      Rails.logger.info "USUARIO LOGADO - #{current_user.email} - #{current_user.role}"
      Rails.logger.info "####################################################################################"
      if current_user.role == "user"
        redirect_to inicio_path
      end      
    else
      Rails.logger.info "####################################################################################"
      Rails.logger.info "USUARIO NÃO LOGADO USUARIO NÃO LOGADO USUARIO NÃO LOGADO USUARIO NÃO LOGADO USUARIO "
      Rails.logger.info "####################################################################################"
      redirect_to inicio_path
    end 
  end  
end