I've never used ROMs personally. I'm a bit of a purist in that I think using the original hardware is part & parcel of the experience- you're supposed to fiddle with an NES cart to get it to work, you're supposed to hear the Dreamcast's drive revving up and down, etc.
Having said that, I have zero issues with people using ROMs in 99.9% of their applications. An example: I love The Guardian Legend on NES. I'd like other people to experience playing the game. How does one legally buy the game, so that the original developer gets their share of the money? Answer- they DON'T. There isn't a way to buy that game nowadays- it's not on a compilation, it's not in the NES mini, it's not on Virtual Console, nothing. So- pirate away! No one is losing money here, not even the Ebay resellers with original carts- they cater to a collector market, not a player one.
That's how most games are- they aren't available for purchase in the modern era, and they never will be. People claim that 'oh, but the value goes down on pirated games so they don't make money if they're re-released!' Bull. We buy re-releases all the time. I own 3 bloody versions of Shadow of the Colossus. If the games are good, the re-release will sell. If they aren't, then they're already worthless so who cares? All of this ignores possible fair use transformations, like hacks and translations, that are only possible via ROM.
Now, I do draw the line at one point- if the game IS readily available to be bought, then I don't think getting a ROM is appropriate. Anything in the 3DS virtual console, anything on Steam or GOG, even the games in the NES & SNES minis, should be purchased. "But I don't own or want a 3DS!" Too bad. Console exclusives have always been around. You want to play God of War? You get a PlayStation. You want to play Mighty Bomb Jack? You get a 3DS & download it.
With EmuParadise gone, I doubt it'll ever happen, but man I wish one of these sites would actually make Nintendo or whoever is after them go to court and explain why decades olds software they don't, won't and possibly can't sell, shouldn't be distributed via non-commerical means. I'd hope the court would tell them to put it out there themselves, or let it go.