First, can someone explain what the gamelist.xml file does and why it is in every rom folder?
It seems that in the process of adding and deleting roms a few of my folders are now missing the gamelist.xml file. I probably deleted it by accident.
What is the proper way to add and edit it if needed?
In EmulationStation interface, juste Update the list game in the Games menu.
You only need it if you're scraping games. I would suggest using this to scrape your games from desktop and then transferring the gamelist.xml and stuff over.