For some reason it doesn't accept 5 arguments as said in http://apidock.com/rails/v4.0.2/ActionView/Helpers/FormHelper/check_box

fields_for checkb_ox

<%= form_for @user, url: admin_user_path(@user) do |f| %>

	<%= f.label :name %>
	<%= f.text_field :name %>
	<br>
	<%= f.label :email %>
	<%= f.text_field :email %>
	<br>
	<%= f.label :roles %>
   	<%= f.fields_for :roles do |roles_fb| %>
	   	<% @user.roles.each do |k,v| %>
	      <br>
	      <%= roles_fb.label k %>
	      <%= roles_fb.check_box k, v, {}, 'true', 'false' %>
	    <% end %>
	 <% end %>
	<br>
	<%= f.label :blog_url %>
	<%= f.text_field :blog_url %>
	<br>
	<%= f.label :short_bio %>
	<%= f.text_field :short_bio %>
	
	<br>
	<%= f.submit "update", placeholder: "Update" %>
	
<% end %>

#Error
ActionView::Template::Error (wrong number of arguments (5 for 1..4)):
    11: 	   	<% @user.roles.each do |k,v| %>
    12: 	      <br>
    13: 	      <%= roles_fb.label k %>
    14: 	      <%= roles_fb.check_box(k, v, {}, 'true', 'false') %>
    15: 	    <% end %>
    16: 	 <% end %>
    17: 	<br>
  app/views/admin/users/edit.html.erb:14:in `block (3 levels) in _app_views_admin_users_edit_html_erb__4448456006841906648_70111123066320'
  app/views/admin/users/edit.html.erb:11:in `each'
  app/views/admin/users/edit.html.erb:11:in `block (2 levels) in _app_views_admin_users_edit_html_erb__4448456006841906648_70111123066320'
  app/views/admin/users/edit.html.erb:10:in `block in _app_views_admin_users_edit_html_erb__4448456006841906648_70111123066320'
  app/views/admin/users/edit.html.erb:1:in `_app_views_admin_users_edit_html_erb__4448456006841906648_70111123066320'
  app/controllers/admin/users_controller.rb:73:in `edit'


  Rendered /Users/borjagvo/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (76.2ms)
  Rendered /Users/borjagvo/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (76.2ms)
  Rendered /Users/borjagvo/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (0.8ms)
  Rendered /Users/borjagvo/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (0.8ms)
  Rendered /Users/borjagvo/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/template_error.html.erb within rescues/layout (84.7ms)
  Rendered /Users/borjagvo/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/actionpack-4.1.4/lib/action_dispatch/middleware/templates/rescues/template_error.html.erb within rescues/layout (84.7ms)