Add a Custom Body Class Based on the Logged-in User Role

/**
 * Add user role as a body class
 */
function custom_add_user_role_body_class( $classes ) {

    if ( is_user_logged_in() ) {
        $user = wp_get_current_user();

        foreach ( $user->roles as $role ) {
            $classes[] = 'user-role-' . sanitize_html_class( $role );
        }
    }

    return $classes;
}

add_filter( 'body_class', 'custom_add_user_role_body_class' );