This is not a good question because the 2 main panels works in the same environment.
Roundcube use IMAP to browse mailboxes so it able to connect to the Zarafa server in order to provide a webmail.
So you can use Zarafa AND roundcube panel to display content of mailboxes.
The opposite is not the same : Zarafa panel use the MAPI php library so the Zarafa webmail is not able to connect to a standard IMAP mailbox server...
