ROMs are illegal. It's simple. You're violating a copyright restriction of the companies. The only
exception is home made ROMs. You might here stuff on other sites like, "you can only keep the ROM for 24 hours." or
"it's only legal to own them if you own the original game." Let me make this clear: it's BULLSHIT. Owning ROMs
is illegal on any condition. Emulators are legal.
Now there's another side to the story. If you don't download them off file-sharing sites you won't get caught.
Also people have stopped caring if you download older games. The only thing companies really care about is if you download
new games. Basically, nobody cares if you download a ROM and your never going to get caught.