What's authentic pasta? Pasta is just flour, egg and water, it's a bit difficult to go beyond that as you'll end up with something else!
Touristy restaurants are to be found in touristy areas. You're just as likely to find good, authentic Italian food there but you'll be paying a premium for it. I've had good meals in Rome and not so good meals. The majority of the good ones have been away from the major tourist sites, usually down a side street somewhere.
I've found that it's pointless asking for recommendations for a restaurant as it's such a subjective matter. People's tastes are so different that often what one considers good another considers poor. I would never take the advice of a stranger on the internet, the only recommendations that I go by are those from friends as we both know each others likes and dislikes and we tend to have the same idea of what constitutes a good meal or not.
You'll also hear people suggest going where the locals go but how do you know where they go? You can't tell by looking into a restaurant whether the people in there are locals or not. Some may be speaking Italian but they may be tourists from other parts of Italy and know just as much about the restaurant as you do.
I tend to follow my gut instinct. I'll check out other people's meals (particularly if they're seated outside), look at the menu, if there are too many dishes then it's a fair bet that most of them will be pre-prepared or bought in. I tend to avoid the older, well established venues as I find they've become stuck in their ways and possibly resorted to short cuts or cheaper ingredients. I regularly find wherever I go that the best meals I've had have been in newer establishments, places where the kitchen staff are young and keen and really motivated in cooking excellent food and making a success of their business.
For me, if I was visiting Rome purely on an gastronomic basis I would eat little and often at various places. It's far too easy to get carried away at lunch time and find yourself too full to eat dinner. Therefore don't eat like the Italians with multiple courses at lunch, often including a filling pasta dish, but spend time wandering around having a slice of pizza somewhere, a bar for some light snacks, a gellato here and there, sampling meats and cheeses in various deli's before settling down for a decent meal somewhere in the evening.
Don't go with a list of recommendations from random strangers. Just go and explore, part of the fun is stumbling upon some hidden gem. You know what you like and you should be able to get a good idea if somewhere suits you by looking at it.