We were in Rome for 11 days earlier this month. I specifically wanted to go to Slow Food restaurants, and we managed to get to only one. It was Osteria del Velodromo Vecchio, at Via Genzano, 139 , Telephone 06 7886793. We paid 77 including wine for 2, and it was very good and a lot of food. It is not in the central city but you can get there by: Metro stop Colli Albani. Plan on asking them to call a taxi to get beck to where you are staying. It was the best meal we had in Rome and I doubt youll find a tourist here very often.
We also liked Ostaria I Buoni Amici, Via Aleardi, 4. Just off Via Merulana right near San Giovanni in Laterno and within walking distance of the Coloseum. Also near Manzoni metro stop, Telephone 06 7049199. It was 100 for 3 people. It is recommended in Lets Go but its not full of tourists because of it is located away from the top 10 sights. We have eaten there before and like it a lot. Closed Saturday and Sunday
Also recommended in Lets Go is Hostaria da Nerone, very near the Coloseum, Via delle Terme di Tito 96, (go upstairs at the Metro stop to the little park, cross the footbridge. Walk down Via del Monte Oppio, make a left turn at the corner and there is Nerone.) Telephone 06 4817952. We didnt go there because of the Lets Go recommendation--We went there because my cousin lives right there and its her neighborhood eatery. Again we have been there several times over the years. It was 135 for four people including the house wine. Closed Sunday
Finally, a place which we like is Trattoria Colli Emiliani, Via Tiburtina, 70, 064453622. We spent 38 on house wine, mineral water, 3 antipasti, 2 primi, and 2 secondi, which was a nice lunch for 4. This is North of the train station at the back end. Metro Stop: Vittoriogo one block south east from the end of the Piazza (actually a park to Via Cairoli and go toward the Termini train tracks, go through the underpass and you come out at Piazza Tiburtina, Its two blocks further on the right of Via Tiburtina. I doubt youll find a tourist in this place.