I noticed that this cron:
iRedMail: Cleanup Roundcube SQL database
2 2 * * * /usr/bin/php /opt/www/roundcubemail/bin/cleandb.sh >/dev/null
was failing with "/bin/sh: 1: /usr/bin/php: not found". I was able to discover that the php5-cli package didn't get installed originally, not sure if this was just a mistake or on purpose. I installed php5-cli and the crontab now completes without an error. It's a fresh install of iRedmail-0.9.5.