class RoutesController < ActionController::Base
  before_filter :authenticate_user!
 
  def root
    root_p = case current_user.role
      when 'admin'
        SOME_ADMIN_PATH
      when 'manager'
        SOME_MANAGER_PATH
      else
        SOME_DEFAULT_PATH
      end
 
    redirect_to root_p
  end
end

在您的routes.rb中：

root 'routes#root'

附：示例期望使用Devise,但您可以根据需要自定义它.