I have terrible but defined habits for my ROMs. I use the same folder structure for all of them.

./[platform]/[game]/[game].zip

./[platform]/[game]/[game].iso

./[platform]/[game]/saves/…

If it’s a series, using Pokémon as an example, I also have:

./Pokemon/Backups/[game].zip

./Pokemon/[generation]/[game]/[game].iso

So it’s not that good of a backup, mainly there in case the iso corrupts, but I think it’s better than nothing.

It did add an international arms market, where you can trade excess things for civs.