The place via Leonina is fantastic, a small street just a couple of minutes walk from Coliseum and Trajan's Forum; also there are many nice restaurants with excellent Italian food and delicious little Italian sweets cafes just in front of the doors!
Michele is a great host, very helpful and friendly; the apartment terrace, full of green plants, is an excellent place for breakfast with the view of nice Roman roofs and seagulls passings by. Very romantic! Also, it is possible to have a good sleep as if you go to bed late at night (or morning), nobody bothers at the early hours - it is so quiet that you can sleep until noon ;).
I really recommend this place!