Roundcube allows you to synchronize your contacts with a CardDAV server, through a third party plugin. Using a CardDAV server like Radicale or owncloud's "Contacts" application, both available in YunoHost, allows you to centralize and manage your contacts.
Similarly to IMAP that allows you to synchronize your emails with your mail server, CardDAV allows you to access your contacts through multiple clients, such as Roundcube.
Thanks to CardDAV, you will not have to import your contacts in each of your devices.
* Look for Plugins section using the nano search function (Ctrl-W) and identify the line beginning with `$rcmail_config['plugins'] = array('carddav','http_authentication', 'archive', 'new_user_identity'`
Now, you just have to connect to your Roundcube application, select "Parameters" located at the top right corner, then select "CardDAV" in the left panel.
* Go to "Contacts" section of your owncloud application and click on the gear wheel icon located at the bottom left. Then, click on "CardDAV link" and copy the URL that appeared.