You can set up N64FlashcartMenu to load a specific ROM directly instead of booting up the menu's graphical user interface.
To use the autoload function, open the N64 ROM information screen on any ROM, then press the R Button on your Controller and select the Set ROM to autoload option. When you restart the console, N64FlashcartMenu will now only load the selected ROM, rather than the menu itself.
NOTE: If you want to return to the menu, press and hold the START Button on your Controller while turning the console's POWER button to the ON position.