We loved the location of Federico's place, as well as the rooftop terrace. We did not deal with Federico, though, as he was out of town. We instead dealt with Laura who was a responsive and helpful host.
The location is perfect. You are steps away from a beautiful square with one of the oldest churches in Rome. There are tons of places to eat and drink at right outside the front door. We spent a lot of time in the square just sitting at an outdoor restaurant, having drinks and taking in the sights.
As an apartment, the rooftop terrace is the best feature. The apartment itself is minimal. It reminded us of a college dorm. It had a studio layout, with a separate bedroom. Book this place for the location and the rooftop terrace.