That is not correct at all, at least not in the US.
1. While US Copyright Law Section 117 does allow you to make backups of your media, the law clearly states that the owner must make the copy or authorize someone else to make the owner a copy of the owner's media. But US law prohibits the use and ownership of devices and software that create game ROMs. So while you can legally own a ROM you created, you cannot legally make one because you cannot legally own anything that helps create a ROM. Basically, this all sums up to the fact that ROMs are illegal in the US, even if it is in a round-about way.
2. In Atari v. JS&A, the US District Court said games ROMs are not covered by US Copyright Law Section 117. This is because S117 is to protect the owner against deletion, corruption, etc. The court ruled that video games are not easily erased, so they are not covered. It went on to say that games ROMs are illegal even if the owner makes the copy himself.
And by the way, that rumor about a 24-hours evaluation period is complete BS. Someone just made that up to feel better about their own piracy.
All this goes right out the window if the copyright holder allows users to copy the game, which happens but is still fairly rare.