Every emulator will tell you to acquire your ROMs legally.

It's of course possible to acquire the N64 Verilog legally too.

I'm not sure if you're being sarcastic, because I'm not aware of any ways to do this save for writing the Verilog from scratch.

Legally speaking, you could have legit access to the verilog by working for one of the existing licensees - eg Nintendo, chip companies, fab companies. Or by buying or otherwise acquiring (eg patent trolling settlement) a license to it from Nintendo.

It's not really likely, but it's within the realm of possibility. Somewhat less likely than legally acquired game ROMs, sure, but only a matter of degree...