Roundcube is not available on Jessie except in backports.  This role is
also out of date and needs reviewed and updated for the release included
in backports.  Roundcube could alternatively be installed from source as
recommended by the maintainers.

Make a clean distinction between Debian 7 and Debian 8.  Anticipate the
next Ubuntu LTS release (Xenial) that is planned for support.

Not awesome. We need a better alternative, ideally one with a better security stance.