Some older RetroArch Vita builds require the BIOS to be placed directly in the same folder as the game ROM . However, the modern standard (as of RetroArch 1.9.0+) is the system folder. To be safe, place them in BOTH the system folder AND the ROM folder.
PlayStation Vita , BIOS files are the essential "system software" that allows RetroArch's cores (emulators) to function correctly. While 8-bit and 16-bit systems like the NES and SNES often run without them, more complex systems—including the PlayStation 1 Game Boy Advance bios files for retroarch ps vita