I don't know the full extent of the problem, but it seems like you could create a script that would first launch RetroArch and then after a wait, send a network command to load the game. You could then create a launch command in /opt/retropie/configs/emulators.cfg that would launch the script and apply it to the ROM. Granted, this is a very involved solution and there might be a better way. Out of curiosity, why are you opposed to simply launching the games with a core that will run them?
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