application_controller.rb

   protected
    def check_perms
      #logger.info "------------------\n"
      #logger.info controller_name
      #logger.info action_name
      #logger.info current_user.role.permissions.fetch(controller_name).index(action_name)
      #logger.info "------------------\n"

      if current_user.role.permissions.fetch(controller_name).index(action_name).nil?
        flash[:warning] = "You do not have permission to do that."
        redirect_to current_user
      end

    end

random_controller.rb

  before_filter :check_perms, :only => [:edit, :update, :new]

random_view.html.erb

<% if current_user.can?("foobar", "edit") %>
some stuff here
<% end %>

role migration

class CreateRoles < ActiveRecord::Migration
  def self.up
    create_table :roles do |t|
      t.string :name
      t.text :permissions

      t.timestamps
    end
  end

  def self.down
    drop_table :roles
  end
end

Role.rb

class Role < ActiveRecord::Base
  serialize :permissions
  has_many :users
end

User.rb

  belongs_to :role


# permissions
  def can?(controller, action)
    begin
      self.role.permissions.fetch(controller).index(action).nil? ? false : true
    rescue
      false
    end
  end