I have an Ubuntu 12.04 server that has a successful redmine install on it. I have been using redmine on it for a while, but when I tried to set up the SSL cert using this method, https://www.digitalocean.com/community/articles/how-to-create-a-ssl-certificate-on-apache-for-ubuntu-12-04.
My https:// version of the site just shows my "index of /" instead of the actual site. If I go to the old http:// it still successfully shows the site. The only thing that I've done which isn't standard practice (to the best of my knowledge) is to change my default DocumentRoot in /etc/apache2/sites-available to /var/www/redmine, from the standard /var/www/.
I have made sure that my pages default-ssl document root is also /var/www/redmine (which is where my symbolic link to the actual redmine folder is).
If you need anymore information I'd be happy to post it. Thanks,