Michael Schumacher was the driver to beat at Monza on Friday morning while Ferrari had a few concerns after Fernando Alonso was forced to park his car.
With the sun shining down on the Monza track, Practice One got underway for the Italian Grand Prix with Ferrari's Felipe Massa posting a 1:28.370 ahead of Lewis Hamilton and Charles Pic. The trio, though, clocked their times in extended installation laps rather than while down to serious running.
After a brief lull in the action when the drivers reported back to their teams and were given last minute instructions the silence was broken by Kimi Raikkonen and Ma Qing Hua with the Lotus driver taking first place with a 1:28.175 and the Chinese debutant too much of the first chicane.
Hamilton was the next to lead the way before he was dropped by Fernando Alonso, who clocked a 1:26.072 to great applause from the gathered tifosi. His reign was short-lived as Michael Schumacher hit the front, 0.111s up on the Ferrari driver while Jenson Button put his McLaren into second.
That prompted a brief battle between the three as they traded positions ending with Schumacher top with a 1:25.422, Button 0.434s down and Alonso a further tenth off the pace as the trio back into the pits after their first run of the day.
With many drivers sporting scrapped bargeboards given the unforgiving Monza kerbs, there were a lull ahead of the final 30 minutes as they discussed various aspects with their teams and changes were made to the cars.
The drivers ventured out again in the final 30 minutes but the lap times were not as quick as earlier as they put in the mileage, still on the harder of the two Pirelli tyres. There was an early shower for Alonso as the Ferrari driver's transmission seemed to give up the ghost, forcing him to pull down an escape road and park it with six minutes remaining.
Alonso was joined on the sidelines by Pastor Maldonado as the Williams driver stopped on the side of the track and checked his rear wing before walking away from his stricken car.
The session ended with Schumacher quickest of all with a 1:25.422, 0.301s up on Button and a further 0.039s ahead of Rosberg.
01 Michael Schumacher Mercedes 1:25.422 26 laps
02 Jenson Button McLaren 1:25.723 0.301 29 laps
03 Nico Rosberg Mercedes 1:25.762 0.340 26 laps
04 Fernando Alonso Ferrari 1:25.800 0.378 22 laps
05 Felipe Massa Ferrari 1:25.861 0.439 27 laps
06 Lewis Hamilton McLaren 1:25.944 0.522 30 laps
07 Kimi Raikkonen Lotus 1:26.046 0.624 25 laps
08 Sergio Perez Sauber 1:26.323 0.901 26 laps
09 Mark Webber Red Bull 1:26.390 0.968 24 laps
10 Pastor Maldonado Williams 1:26.504 1.082 19 laps
11 Sebastian Vettel Red Bull 1:26.508 1.086 18 laps
12 Nico Hulkenberg Force India 1:26.518 1.096 21 laps
13 Valtteri Bottas Williams 1:26.641 1.219 26 laps
14 Kamui Kobayashi Sauber 1:26.746 1.324 23 laps
15 Jerome d'Ambrosio Lotus 1:27.180 1.758 29 laps
16 Jules Bianchi Force India 1:27.192 1.770 22 laps
17 Daniel Ricciardo Toro Rosso 1:27.373 1.951 25 laps
18 Jean-Eric Vergne Toro Rosso 1:27.789 2.367 24 laps
19 Heikki Kovalainen Caterham 1:27.855 2.433 27 laps
20 Vitaly Petrov Caterham 1:28.578 3.156 20 laps
21 Charles Pic Marussia 1:28.751 3.329 26 laps
22 Timo Glock Marussia 1:29.207 3.785 21 laps
23 Pedro de la Rosa HRT 1:29.331 3.909 21 laps
24 Ma Qing Hua HRT 1:31.239 5.817 26 laps