I had a great stay at Rossana's place, with many thanks to Francesco as well. The hosts were very kind and made me feel at home right away. Situated at a busy thoroughfare, the room was neat and sufficiently equipped with a private bathroom and airconditioning.
Rossana's place is located a bit outside the main tourist attractions on the east side of the Tiber, but very close to the Vatican (with its awesome museum; don't miss it, but try and book a ticket for the occasional evening opening if possible), and within walking distance of the old city centre. Don't forget to enjoy the quiet of St. Peter's square at night (when all day tourists have gone), and to have a passeggiata up the Gianicolo, which allows for great panoramic views of the city. I warmly recommend Rossana's bed and breakfast.