sync user roles across WordPress Multisite:

<?php
function wpmu_sync_user_roles( $user_id, $role ) {
    // is_multisite() used just as precaution, this code is meant to Multisite only
    if( ! is_multisite() || ! is_main_site() ) {
        return;
    }

    // if( get_current_blog_id() == $id ) {}
    // $blogs = $wpdb->get_col( "SELECT blog_id FROM $wpdb->blogs" ); // get all blogs via sql
    $blogs = get_blogs_of_user( $user_id );
    $original_blog_id = get_current_blog_id();

    unset( $blogs[ $original_blog_id ] ); // remove main site from affected sites

    foreach( $blogs as $blog ) { // iterate through blogs of user
        switch_to_blog( $blog->userblog_id ); // switch to another site

        $site_user = get_user_by( 'id', $user_id );
        $site_user->set_role( $role ); // update role like on main site
    }
    restore_current_blog(); // return to current site
}
add_action( 'set_user_role', 'wpmu_sync_user_roles', 10, 2 );
?>

Sync all roles with capabilities on all sites of the WordPress Multisite Network:

<?php
global $wpdb, $wppa_roles;
if ( is_multisite() && is_super_admin() /*&& $wppa_apply_to_all*/ ) { // sync user roles !!!!!!!!!!!!!!!!!!!!!!!!!!!!
	$blogIds = $wpdb->get_col( "SELECT blog_id FROM $wpdb->blogs" );
	$user_capabilities = get_option( $wpdb->prefix.'user_roles');
	foreach( $blogIds as $blog_id ) {
		switch_to_blog( $blog_id );
		$wppa_roles = wppa_getUserRoles();
		$option_name = $wpdb->prefix.'user_roles';
		$result = update_option( $option_name, $user_capabilities );
	}
	restore_current_blog();
	$wppa_roles = wppa_getUserRoles();
}


function wppa_getUserRoles( $wppa_object='role' ) {
	global $wp_roles;

	if( ! isset( $wp_roles ) ) {
		$wp_roles = new WP_Roles();
	}

	if( 'role'===$wppa_object && function_exists( 'bbp_filter_blog_editable_roles' ) ) {  // bbPress plugin is active
		$wppa_roles = bbp_filter_blog_editable_roles( $wp_roles->roles );  // exclude bbPress roles
		$bbp_full_caps = bbp_get_caps_for_role( bbp_get_keymaster_role() );
		// add bbPress keymaster caps to Administrator role
		$wppa_roles['administrator']['capabilities'] = array_merge( $wppa_roles[ 'administrator' ]['capabilities'], $bbp_full_caps );
	}else{
		$wppa_roles = $wp_roles->roles;
	}

	if ( is_array( $wppa_roles ) && count( $wppa_roles ) > 0 ) {
		asort( $wppa_roles );
	}

	return $wppa_roles;
} // end of wppa_getUserRoles()
?>