@Shaolinmonk Thanks, all noted.
This all depends on the version of RetroArch that you have installed (32-bit, 64-bit, sideloaded, etc.). We've done our best to include every possible option with every recent version of RetroArch. If there really are any cores in the most recent versions of RetroArch that are not listed in LaunchBox, please let me know what they are. We're not aware of any.