Add user roles as classes to body tag in front and backend.

add-roles-to-body.php

<?php
/**
 * Add user roles as classes to body tag in front and backend.
 */
add_filter( 'body_class','add_roles_to_body' );
add_filter( 'admin_body_class', 'add_roles_to_body' );
function add_roles_to_body( $classes ) {
	global $current_user;

  foreach ( $current_user->roles as $user_role ) {
  	// body classes are built differently on the front and back end.
  	// https://core.trac.wordpress.org/browser/tags/3.8.1/src/wp-admin/admin-header.php#L164
  	if ( ! is_admin() ) {
  		$classes[] = 'role-'. $user_role;
  	} 
  	else {
  		$classes .= 'role-'. $user_role;
  	}
  }
		
	return $classes;
}