consider adding the following to /usr/local/lib/roundcubemail/config/config.inc.php ?
$config['htmleditor'] = 1; # enables html editor by default
$config['show_images'] = 2; #displays images by default
$config['session_lifetime'] = 480; #changes session auto log off to 8 hours ( guess this is debatable)
$config['login_rate_limit'] = 5; #rate limits 5 attempts to log into roundcube before banning you for 1 minute
$config['search_mods'] = array('*' => array('subject'=>1, 'from'=>1, 'to'=>1, 'cc'=>1, 'bcc'=>1, 'body'=>1)); # enables search that works much better by default