Yeah there’s a fast forward button. RetroArch isn’t an emulator as such, or at least not in the same way others are, I don’t quite understand how it all works but you choose your emulator core and different cores have different settings. So if you don’t like the FF of one core, just change your core. I’m not sure it saves carry over when changing cores so maybe experiment when core settings before making any progress in the game.

I’ve been using melonDS for SoulSilver and it’s been great, FF is probably 2x speed on that one. It might be adjustable, I’m not sure. When I was playing Crystal the FF was probably closer to 10x speed, it was a bit much. But there’s lots of choices for cores so you can play around with it and see what you like.