For the uninitiated, Retrobat is a frontend based on the popular EmulationStation Desktop Edition (ES-DE). Think of it as a "plug-and-play" operating system for emulation, without needing to dual-boot into something like Batocera or Lakka.
Put ROMs in RetroBat\roms\[systemname] . Supported extensions vary (e.g., .nes for NES, .iso for PS1). retrobat full