The loft was incredibly comfortable and Giulia is a fantastic host. Very prompt with communication, and exceptionally helpful!
The BnB is very near public transport (which you will need to use to get to the city centre). It takes about 20 mins (excluding wait time for the bus to arrive) to get to the Colosseum. It would be best to get a transport pass from the Tabacchi nearby (there a several different types of passes available; choose one according to duration of stay).
Giulia is always at hand to answer all questions. The information booklet she has created will be one of the most useful things during your stay.