I hade the same problem, and i read the suggestions.
actually i read urbanx suggestion and found that it was the same.
in config.main.inc.php
i found something that when changed solved the problem for me and here is the solution:
Actual file:
// store sent message is this mailbox
// leave blank if sent messages should not be stored
$rcmail_config['sent_mbox'] = 'Sent';
// move messages to this folder when deleting them
// leave blank if they should be deleted directly
$rcmail_config['trash_mbox'] = 'Trash';
// display these folders separately in the mailbox list.
// these folders will also be displayed with localized names
$rcmail_config['default_imap_folders'] = array('INBOX', 'Drafts', 'Sent', 'Junk', 'Trash');
// automatically create the above listed default folders on login
$rcmail_config['create_default_folders'] = [COLOR=Red]FALSE[/COLOR];
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CHANGE THE
FALSE TO
TRUEthis should automatically allow roundcube to automatically create the listed default folders on login
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give me an update on what happened and if it did work with you so that also others could find it useful.

Good Luck.
Best Regards,
smalek.
