You must dump this from your physical PS1 console using a memory card exploit or specialized hardware.
Technically, there isn't one single file named "rom.bin" that contains every game. Instead, the term usually refers to one of two things in the emulation community: ps1 rom.bin
Many emulators require a PlayStation BIOS file (often named something like SCPH1001.bin ). This file acts as the "brain" of the console, containing the original startup code required to boot games. Without this "ROM" file, most emulators cannot function. You must dump this from your physical PS1