I have a really old blog post (predating all the modern ROM SIMM developments) about how to hack the IIci ROM to add a sampled startup chime. I’d imagine the process on the IIsi ROM used in the ROM-inator II would be similar. It’s not exactly the same, since things are likely moved around. It might give enough hints for someone to figure it out.
www.downtowndougbrown.com
It would be cool to make a utility for automatically adding patches like this to the ROMs…