Hamilton, Rosberg in complete control in Bahrain
Lewis Hamilton drives in the third practice session for the Formula One Bahrain Grand Prix at the Sakhir circuit in Manama on April 5, 2014 - by Marwan Naamani
Hamilton, who was fastest on Friday, clocked 1:35.324 with Rosberg, the current championship leader, repeating his second place from the previous day on 1:35.439
Although there was just a fraction between the two teammates, Sergio Perez, in a Force India, was half a second off Hamilton's pace in third.
It all pointed to another dominant weekend for Mercedes after Rosberg took the season-opener in Australia and Hamilton led from start to finish in Malaysia.
However, it was a dismal session for reigning world champion Sebastian Vettel who span off the course and into the gravel in his Red Bull, managing a poor time of 1:39.225, the second slowest of the session.
Hamilton, the 2008 world champion, will be aiming for a third successive pole position in qualifying later Saturday.
If he is successful, it will be the 34th of his career and will take him past Jim Clark's British record.
The top six in practice on Saturday was rounded off by the two Williams cars of Finland's Valtteri Bottas and Brazilian veteran Felipe Massa, twice a winner on the Sakhir circuit in his Ferrari days.
Britain's 2009 world champion Jenson Button was sixth fastest as he takes part in his 250th grand prix this weekend.
Vettel's Australian teammate Daniel Ricciardo was 13th quickest in 1min 37.119sec but he will be demoted 10 places on the grid from wherever he qualifies following a penalty for an unsafe release from a pit stop in Malaysia.