It's believed by many that there are exceptions or loop holes that make ROM's legal under specific circumstances these beliefs are wrong, if you download a ROM your essentially stealing and or taking/receiving stolen property, owning a copy of the game then downloading a ROM of it would be pretty much the same as buying a copy of a game then afterward stealling another copy of the same game from the store, I don't know very much about the playstation emulator but depending on what games it has available, it could be legally contracted with those who own the rights to the games available making it a legal means of acquiring vintage games but if it has access to Nintendo property it would very likely fit into the category of illegal emulation.
