I just set up Roundcubemail on the Fedora+Postfix server. There is an array of not so great tutorials but I found a good one which is complete. Here is the link:
Easy Setup of Roundcubemail
Came across one issue where mail could not be deleted.
Had to edit the following directive in /etc/roundcubemail/main.inc.php
$rcmail_config['create_default_folders'] = TRUE;
Restart all related services.