do you mean bsnes inside retroarch ? i'm currently using retroarch with bsnes core to do it on my system like this:
this an excerpt from my emulator cfg file
executable M:\Emulation\Emulator_programs\retroarch\retroarch.exe
args -L M:\Emulation\Emulator_programs\retroarch\cores\bsnes_libretro.dll "M:\Emulation\Emulator_programs\retroarch\system\Super Game Boy (World) (Rev 2).sfc" --subsystem sgb "[romfilename]"
rompath M:\Emulation/Emulator_roms/Nintendo_Super_GameBoy
romext .zip;.gba;.gbc;.gb
system Nintendo Super Game Boy
i hardcoded the super game boy sfc rom in the arguments and can select (super) gameboy files to launch the games.