Ronaldo missed a few good opportunities to get off the mark for his new side, whom he joined from Real Madrid in a £100m transfer during the summer window.
The Portugal international netted in each of his last 10 La Liga outings for Madrid, but it was left to his teammates to earn Saturday's dramatic 3-2 victory at Stadio Marc'Antonio Bentegodi.
Allegri had no complaints with the club-record signing's display, however, telling Sky Sport Italia: "His hold-up [play] was good. Unfortunately, he didn't score a goal. He worked well with the team, I would say he played well. You can see he is different.
"It was a victory that was needed. We know the difficulties this year to win again and these three points are an optimal start. You need to be happy with victories. In the first three games it's important to bring points home."
Ronaldo has scored 658 goals in his professional career for both club and country, seeing him lead the way for both Madrid (450 goals) and Portugal (85).