Seems I had a problem with permissions, when following the github wiki I was using the mount command with SUDO, and ofcourse the owner/group was root so the user pi couldn't read the mounted dir, the fix was to include the UID and GID for PI in the options during the mount command
sudo mount -t cifs -o domain=workgroup,username=<USERNAME>,password=<PASSWORD>,nounix,noserverino,defaults,users,uid=<LINUX_USERID>,gid=<LINUX_GROUPID> //<HOSTNAME>/ROMSSHARE /home/pi/RetroPie/roms
both LINUX_USERID and LINUX_GROUPID were 1000 in my case.
Hope this helps someone from wasting as much time as I have on this problem.