You need to be able to configure samba as a PDC in order for it to act as a domain, thus store profiles on it. However you will find home profiles that are free to grow will be too big for network storage. So you it may be better just to schedule backups of the profiles to the NAS drive.
More information on configuring samba can be found here: http://us5.samba.org/samba/
If the NAS drive is locked and you cannot SSH into it then you are locked to the manufacturer’s defaults, which won’t allow you to modify the samb.conf file.
Hope this helps.