How to configure Samba to allow root user for full control to the particular share?

Do you have a password set in Samba (not in the system passwd file) for root ? You should be able to set such a password by running smbpasswd -a root.

You should be putting up your smb.conf so that we can actually assess the problem. Anyway here's a hint:

   invalid users = root

is part of the default smb.conf.

Well then. Is root a valid smbuser, yet? Then try explicitly allowing root :

valid users = root 

And try something like this:

[config]
    comment = Admin Config Share  - Whatever
    path = /
    valid users = someusers, somegroup
    force user = root
    force group = root
    admin users = someusers, somegroup   
    writeable = Yes

if you can't access two users, one for a regular user and the other for a root, you need to alias the netbios in smb.conf file so that windows sees them as two servers. Then access each with a different user id. You may also add to the windows' host file the same server's ip with different names. The issue is with Windows that can only allow one user at a time, thus cannot access as a root.