I have no idea what "rice-a-roni" is. It sounds like some kind of macaroni cheese but made with rice pasta instead of durum wheat pasta. To be fair, I'm not the best person to ask. I don't buy those kinds of "ready meals". If I want to make macaroni cheese, I boil some macaroni in a pan and I make cheese sauce from scratch, then I combine the two!
I have one word in reaction to the last two posts - YUK! What's wrong with real food, people? ;-)
The etymology of vermicelli is interesting. It means "little worms".
It's the "roni" part of "Rice-a-roni." (Do you have that in the UK?)