RHEL 7 and Samba Permissions in Windows

I can access my RHEL 7 server just fine from my Windows machine. I can create/edit/delete with no problems. One thing I can't do is change the file attributes like the read-only flag.

A file is owned by root and the group for the file is also root.
Owner and group have rwx on the file.
A windows user (let's call it winuser) can do anything to this file except change the read-only attribute.
I have a "winuser" user created on the RHEL server and it has root as its primary group.

The only way I seem to be able to modify the file attributes is to make winuser the owner of the file. Any ideas why?
Even if I change the group for the file to winuser, it still does not allow the attributes to be changed from Windows.

I'm thinking maybe this is a Samba configuration issue? Like I said, from the Windows machine I can do everything else: create/delete/edit. I just can't change the attributes. Am I out of luck here? Is this just not allowed unless the user is the owner?

Thanks.