Carlos Sainz was an impressive fourth fastest for Toro Rosso, six-tenths off Hamilton, followed by the second Ferrari of Kimi Raikkonen and team mate Max Verstappen. Valtteri Bottas finished seventh for Williams, separated from team mate Felipe Massa by Red Bull’s Daniel Ricciardo. Force India’s Sergio Perez completed the top ten.
The session began with a bang - literally. Manor released Rio Haryanto into Romain Grosjean's Haas, and for a moment the two were locked together in an unseemly embrace after colliding. Upon separation, Haryanto got a new front wing and continued, while Grosjean's car was wheeled back to the pits for lengthy repairs to the floor and bodywork.
There were fireworks on track, too. Having briefly gone fastest, Perez went off at Turn 15, just moments after Fernando Alonso had spun his McLaren at the same corner; Felipe Nasr went off at Turn 4 in his Sauber; and Rosberg and Renault's Kevin Magnussen both slid off track and down the escape road in tandem at Turn 13.
With teams running different programmes to make up for the lost track time on Friday, it fell to Red Bull duo Daniil Kvyat and Daniel Ricciardo to set the pace with 1m 28.231s and 1m 28.242s respectively. Mercedes kept their powder dry, Rosberg and Hamilton more than two seconds down the road, with Vettel splitting the two camps.
At the half hour mark Raikkonen went ahead with 1m 27.560s on softs as the track rubbered in. The Finn then cut down to 1m 27.186s, but even so was quickly demoted as Vettel went fastest, also on softs, with 1m 26.911s. Ricciardo then trimmed that to 1m 26.768s on supersofts.
With 25 minutes remaining Mercedes finally hit the front. Rosberg hooked up three purple sectors on softs to go more than half a second faster than Ricciardo, while Hamilton - his first effort compromised by Magnussen's Renault - jumped from 19th to second on softs with 1m 26.328s.
Ferrari responded, with Raikkonen and then Vettel taking over at the top following runs on the supersoft tyre. But with 10 minutes remaining Mercedes too bolted on the red-marked tyre and hit the front once more. Rosberg was first on track and stopped the clocks in 1m 25.800s, but Hamilton bettered that to go 0.176s clear of his team mate, and 0.228s clear of Vettel.
The Toro Rossos got going at the end too, with the impressive Sainz taking fourth and Verstappen sixth, sandwiching Bottas's Williams.
There was some encouragement for McLaren with 11th and 12th for Fernando Alonso and Jenson Button respectively - while behind Kvyat and Sauber's Marcus Ericsson were still within one second of Verstappen, emphasising just how close the midfield battle appears to be in 2016.
WATCH: Haryanto and Grosjean collide in Melbourne pit lane
Unfortunately, we are unable to play the video at this time.
Error Code: UNKNOWN
0:00 / 0:00