Rosberg, Hamilton stamp authority in F1 Malaysia GP practice
Mercedes driver Nico Rosberg of Germany takes part in the first practice session of the Formula One Malaysian Grand Prix, at the Sepang circuit near Kuala Lumpur, on March 28, 2014 - by Ed Jones
Hamilton topped the opening session with his team-mate third, and it was Rosberg, winner the season-opener in Australia, who took control in the later run-out.
Both drivers carried the message, "#TributeToMH370", on their cars as Malaysia mourns 239 people presumed dead in a disappeared passenger jet. Sunday's race will be preceded by a minute's silence.
While Friday practice has little bearing on the race weekend, Mercedes will be pleased to have extended the dominance they showed in Australia -- although it was tight at the top in the second session.
Rosberg's time of 1 min 39.909 was three hundredths ahead of Ferrari's Kimi Raikkonen, with world champion Sebastian Vettel improving to within six hundredths for third spot. The top 11 drivers were all within one second of each other.
Hamilton, who veered off the track in both outings, was fourth in the second session ahead of Ferrari's Fernando Alonso, Williams' Felipe Massa, Red Bull's Daniel Ricciardo and Jenson Button of McLaren.
Lotus's Pastor Maldonado and Caterham's Kamui Kobayashi both sat out the second session for repairs as their dismal start to the season continued.
And Lotus had another setback when Romain Grosjean had to pit early for repairs before returning late on -- when he suffered another problem with his gears and had to retire.
Jean-Eric Vergne span and Nico Hulkenberg, who went fastest early in the second session, ran wide into the gravel as handling problems persisted with this year's new Formula One cars.
"It's really not handling well," grumbled Denmark's Kevin Magnussen, classified second for McLaren in his debut F1 race two weeks ago, while Raikkonen later complained, "My rear tyres are sliding around".
Rosberg hit the front about a third of the way into the 90-minute run and he was later joined by Hamilton at the top of the timesheets as Mercedes showed their superior adaptation to this year's wide technical changes.
But Raikkonen then divided the team-mates as he went second and Vettel also timed quicker than Hamilton as the Red Bull of the four-time world champion, who lasted only a few laps in Melbourne, showed encouraging signs.
Ricciardo is fighting his disqualification from second in Melbourne over fuel irregularities, and his session ended when he ran wide and took an extended trip through the trackside gravel and grass.