That tutorial helps but this works well for me with file server being windows os.
1. Create a blank folder, I like my home folder
2. Edit /etc/fstab
sudo nano /etc/fstab
3. Enter the following on the last line of that file (change to meet your needs)
//HostnameOrIP/h$/roms /home/pi/roms cifs username=username,password=password,iocharset=utf8,sec=ntlm
5. Check to make sure it worked by putting something in that folder on the PC and viewing the contents of the folder on the pi
6. Copy all files and folder structure from original roms folder to mounted folder.
cp -a ~/RetroPie/roms ~/roms
7. Change es_systems.cfg and edit <path> by removing just “RetroPie/” from each object.
sudo nano /etc/emulationstation/es_systems.cfg
8. Reboot again (see step 4)