Roundcube is a browser-based multilingual IMAP client with an application-like user interface. It provides full functionality you expect from an email client, including MIME support, address book, folder manipulation, message searching and spell checking.
1) Login to SSH (Using putty)
2) Backup old roundcube configuration.
cp -R /usr/local/apache/htdocs/roundcube/* /home/roundcube_backup
3) Download latest version of roundcube.
tar zxvf roundcubemail-1.1.3.tar.gz
4) Proceed with the installation
5) Change to correct permission.
chown -R nobody:nobody /usr/local/apache/htdocs/roundcube