I followed this link
I created a backup database copy and I untar the files from roundcube.net.I created a parallel virtualhost like webmailtest.yourdomain.it.
Upload the new files
Use your favorite FTP/SFTP/SCP program to upload the updated files, which are:
skins/* from the release package but don’t replace the entire
plugins folders! You might have added other skins and plugins to those directories which you want to keep.
Also copy the default config file and the mimetypes mapping:
Run the installer
Edit your Roundcube config (
config/main.inc.php for versions < 1.0) and set
'enable_installer' to true. Then open
http://<url-to-roundcube>/installer/in your web browser and click “3. Test config”
Follow the instructions on the screen to update your local config and the database schema.
When you’re done and all the lights are green in the installer, edit your Roundcube config file again and set
'enable_installer' to false if it’s still present. To seal your installation, you should even remove the
installer directory from the webserver.