Did you use the patch with users created before patching? Did you create mailboxes afterwards and check these? It seems to me, that the users you select the new "move" option on, don't have a junk folder. That is the patch on the ispconfig_procmail.lib.php, to create all needed folders for future users. If you have users before who have NO junk folder, it doesn't get created out of the blue. I would advide to set roundcube to create those folders on first connection per default (I think Hans already set the roundcube package up that way) and log into that users via RC to create those missing boxes.
Another possibility would be to create them by hand but watch your permissions closely then!