Edit Roundcube main config(/usr/local/cpanel/base/roundcube/config/main.inc.php)
To change language from English to Portuguese Brasil
Find
$rcmail_config['locale_string'] = ‘en’;
Replace it to
$rcmail_config['locale_string'] = ‘pt_BR’;
You can see the installed languages such as fr(french), en_US(english US) from the folder /usr/local/cpanel/base/roundcube/program/localization.
