Now that, I can't claim to be sure on. I'd still imagine the practice of ripping ISOs off of CDs you own would be every bit as illegal as downloading an ISO of a CD you own, which is: Very.
When you buy a videogame or whatever, you're not buying the software. You're buying a liscense to USE the software, really. As far as I know, you don't have the right to manipulate the software in anyway, unless the developers themselves give you the tools to do so, therefor I believe ISOS ripped by yourself are still illegal.
I know for a FACT ROMs in ALL forms are illegal, regardless if you have the hard copy of the original CD.
The only thing legal about the whole processes are the emulators themselves.