The German, who leads the drivers' standings by 29 points, told reporters: "We're always going to be faster and slower in different parts of the lap relative to each other. Relative to my own lap it was an okay lap and from that second position is still good for tomorrow.
"In the race anything can happen and we need to work towards the race and get a good strategy and have a good race. For the team again, even at a track like Monza, even coming here and being so dominant. There's still the race tomorrow but it's still really awesome for the team."
Rosberg finished second in last month's Belgian Grand Prix, despite colliding with Hamilton at the start of the race.