My E-mail setting is to forward automatically to another E-mail adress.
The roundcube mailbox retains all messages anyway.
Can I set automatic delete in the roundcube inbox?
Roundcube is not a mailbox. It is just a reader. There is no mail "in" roundcube. It simply reads what is in the user's mailbox. If you do not want the mail in the mailbox then why did you create the email account?