Hi Sophle5,
You will not be synchronizing Roundcube to your Outlook but using Outlook to check your e-mail account via IMAP protocol. Roundcube is a browser-based IMAP client application just like Outlook is a client application. They connect to email servers so you can do e-mail.
When configuring Outlook, make sure you select IMAP. The Internet Message Access Protocol (IMAP) allows an e-mail client to access e-mail on a remote mail server. That's how you keep Roundcube and Outlook synchronized. The e-mails are always handled on the server so it looks like they are in "sync" when using different client applications.
Your incoming and outgoing mail server should be provided by your e-mail server administrator. Please contact your provider for details.
From Roundcube (in installations where available) you may check the incoming and outgoing mail server info in Settings -> Account Administration -> MyCloud as shown
here.