.htaccess for roundcube on /var/www/webmail

Hi,
i thounght the .htaccess in /var/www/webmail (for roundcube) worked, but it does not. i dont think i want to change the allow override option in the 000-default vhost file. the apache directives field of course does not work also.

any suggestion, how i can use htaccess for my webmail?

thanks in advance, giftsnake