Follow this to set predefined user. Just grab the package and put it in this directory: program/include/

Package contents:

predefined_user.inc

rcmail_output_html.php

Make your roundcoube be more easily upgraded by using a dynamic dsn e.g.:

$config['db_dsnw'] = 'sqlite:///'.realpath(__DIR__.'/..').'/sqlitedata/roundcubemail?mode=0646';

In this case it does not matter where roundcube is installed. The dsn points to /sqlite/roundcubemail as long as this dir is in roundcube's root.