Cristiano Ronaldo's wonder effort and a Roger Ibanez own goal earned the 2-0 win.
“These are the games where the soul of this group emerges," Bonucci told Sky Italia.
“We knew Roma would keep a lot of the ball, try to spread us and move it around a lot. We knew it'd be tough and we needed the spirit of sacrifice to soak up pressure, then hit them when we needed to."
The lone loss in this calendar year was 2-0 away to Inter in Serie A.
“I think in the Inter game that was our worst possible performance. The men in this group gave their response, so did the coach, by uniting everyone and leaving the outside world behind.
“The great fortune we had was being able to immediately get back on the pitch a few days after that, as we could put it all behind us and get right back on track.
“Now we have a game in hand and we'll be up there."