wp-role-bodyclass.php

// Add role class to body
function ns_add_role_to_body($classes) {
	global $current_user;

	$user_role = array_shift($current_user->roles);
	// 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;
}
add_filter('body_class','ns_add_role_to_body');
add_filter('admin_body_class', 'ns_add_role_to_body');