Hi and welcome to Nethserver Community,
I didn’t test it on NS8 but it should be possible.
You could edit /etc/samba/include.conf to add custom configuration, see also AD LDAP binding error (strong authentification required) - #2 by davidep
It’s also possible to use net conf setparm for configuration, check out Recycle Bin Samba NS8 - #4 by mrmarkuz
Instructions for configuring Roaming Profiles are in the Samba Wiki.
IIRC there’s also a thread about configuring Roaming Profiles in NS7 but I can’t find it.