I am currently running an Ubuntu server and trying to install Roundcube through its web based interface.
I always get an error when i point to the var/www/webmail/installer which says :
"The requested URL /webmail/installer was not found on this server."
Afterwards I decided to copy the files to the var/www/html. I copied all the files there and pointed my browser to the index.php (After deleting the apache html page).
Interestingly enough it worked. I tried to search the roundcube manual about how to troubleshoot this but didn’t find anything.