Valerio's house is really amazing, the decoration is like a mini Rome in doors.
All ver clean near all the places you would like to know. In just 30 minutes you can reach Vatican City and from there return to the house and visit all the most important places in just on day. With Gelatos all the way.
The Coliseo it's just a 10 minutes walking. So the first thing when you arrive it's go to it and familiarize with the environment.
And what to say about Valerio, this guy goes the extra mile to make your experience great.