Those rom paths there are correct though, that bottom image with your folder is Launchbox/Games/Sega Genesis, and in the screenshot above that the path is Games/Sega Genesis which is the same. Its the same in mine, and my setup is on my D drive, but Launchbox doesnt care as its in the Launchbox folder so is a relative path.
The error in your first image is actually saying your emulator path isnt correct, not your rom path.