I'm vegetarian but my husband isn't . I want pasta that is meatless and authentically Roman, where do you recommend?
Easy peasy, Ja!
Most restaurants in Rome, Italy will offer you vegetarian options (learn how to say in Italian 'io sono vegetariana, no mangio carne') as many traditional dishes are made without meat. Do you eat fish? In which case, your options will even be more abundant.
I can recommend you a few of my favourite eateries in Rome:
La Tartaruga cantina (behind sant'andrea della valle) is one of my favs, been going for over 10years. A lunch sandwich at Aristo Campo in campo de fiori is a must for me, as well as baked goods from Il Forno Campo de' Fiori(across the street). Other options include Constanza hosteria at Piazza Paradiso, Pizzeria Remo in Testaccio, Nino at Via Borgognona, Osteria del Belli in Trastevere (great neighborhood for good traditional antipasti restaurants), and the Roman Jewish cuisine (many veggie options) in Ristorante Piperno and Ba'' Ghetto (amazing artichokes and courgette flowers!). For the best gelato, I recommend San Crispino by the chruch of Santa Maria Maddalena near the Pantheon.
Remember that you don't have to order a main dish if you don't find anything to your liking. Instead, get a few vegetarian antipasti and bread (think of it as Italian tapas :)
A few of my favourite Roman pasta dishes:
-- Pasta/pizza bianca: the most basic and yet delicious dish of pasta or pizza (bread) with a light coating of olive oil, a sprinkle of salt and (often) some chilly (peperoncino) flakes. Any restaurant will make this for you.
-- Carbonara/ L'Amatriciana: you are going to want to stay away from these as the dishes are made with pancetta or guanciale (types of Italian bacon) but your husband may like to try the most famous of all Roman pasta dishes
-- Cacio e Pepe: a simple creamy pasta made with pecorino and black pepper.
-- Arancini: fried rice balls. Look for the ones with a pomodoro (tomato), funghi (mushroom) or piselli (peas) filling. Just ask for 'sensa carne' (without meat)
-- Cavalfiori or Brocolli Rabe: a simple pasta recipe with cauliflower or broccoli mixed with an anchovy sauce
It will probably be helpful for you to know some of the basic dishes you will find on menus
-- Carciofi (alla romana): artichokes are Rome's favourite veggie. They are traditionally cooked whole with a sprinkle of olive oil, lemon juice, pepper and salt. Divine.
-- Melanzana: eggplant is another firm favourite. You will easily find main dishes with eggplant, usually grilled with a crispy delicious crust.
-- Asparago: asparagus are popular (both white and green fresh ones) when in season. Sometimes they can be found in the antipasti section of menus prepared simply with parmesan and light dressing.
-- Funghi: mushrooms are prepared on their own and, of course, in pasta and pizza. Another good option is to look for a creamy risotto.
-- Fagioli: beans are very prominent in Roman cuisine. Many kinds (red beans, garbanzo, etc) are used in salads, soups and pastas. Just make sure to tell the waiter you are vegetarian and they will assist with appropriate recommendations.
-- Puntarelle: a kind of bitter kale that is scalded and seasoned with lemon juice and olive oil
Italy is one of the easiest countries in the world in which to be a vegetarian. I am sure you will find many delicious options.
I sometimes read up for recommendations in my favourite blogs. http://www.aglioolioepeperoncino.com/ may be helpful to you as it is written in English and tailored for vegetarians in Rome. You may even want to email the author, she might be able to give you better tips.
Good luck and enjoy!
Mentioned in this answer:
I think the traditional Roman pasta dish, cacio e pepe, is vegetarian. It's quite simple: pasta, cheese and pepper. Otherwise you might try some of these vegetarian restaurants: http://www.eatingitalyfoodtours.com/blog/tag/vegetarian/
I don't think you need a vegetarian restaurant, there are many pasta options without meat.
Margutta RistorArte; Via Margutta 118
A lovely place on wonderful Via Margutta.