I could not get yaba sanshiro to launch full screen through retrofe even with a -f command. Kronos is a branch of yabause and it launches fine using the same arguments, just go into the settings and hide the menubar
executable = emulators\kronos\kronos.exe
arguments = -a -i "%ITEM_FILEPATH%"
here's a list of commands
"-a", "--autostart", NULL, "Automatically start emulation."
"-b", "--bios=", "<BIOS>", "Choose a bios file."
"-c", "--cdrom=", "<CDROM>", "Choose the cdrom device.",
"-f", "--fullscreen", "Start the emulator in fullscreen."
"-i", "--iso=", "<ISO>", "Choose a dump file."
"-nb", "--no-bios" "Use the emulated bios"
"-ns", "--no-sound" "Turns sound off."