Hmm I keep getting a DATABASE ERROR: CONNECTION FAILED!
Here is what I've done.
1) Downloaded roundcubemail-0.2.1.tar.gz - Stable release from http://roundcube.net/downloads
2) Downloaded your "ISPConfig3_for_0.2.1_with" file
3) Uploaded roundcubemail-0.2.1.tar.gz, and "un" tar xvfz roundcubemail-0.2.1.tar.gz
4) Unziped your ISPConfig3_for_0.2.1_with, and uploaded the files in the directorys to the corresponding ones from roundcubemail
5) Renamed the db.inc.php.dist to db.inc.php and main.inc.php.dist to main.inc.php
6) changed the line $rcmail_config .... (in db.inc.php) to $rcmail_config['ispconfig_db'] = 'mysql://ispconfig:password@localhost/dbispconfig';
(note that as password in the above line I used the one found in /usr/local/ispconfig/interface/lib/config.inc.php, and that the password is (md5?) encrypted)
Now when accessing my domain/roundcubemail I get a DATABASE ERROR: CONNECTION FAILED!
Did I miss something here?