On a tense day with intensified security around the Sakhir circuit, Rosberg produced a measured performance to clock the best lap midway through the 90-minutes’ action in one minute and 32.816 seconds.
This lap time left him four-tenths of a second clear of nearest rival Australian Mark Webber of Red Bull who, in turn, was ahead of his team-mate defending champion Sebastian Vettel of Germany.
World championship leader Briton Lewis Hamilton of McLaren, who topped the times in the morning’s opening free practice session, was unable to repeat his pace and struggled to fourth with a revised set-up as the track temperature fell from 40 degrees Celsius to 33 degrees.
Force India sit it out
The Force India team chose to take no part in the second session, instead preparing their cars for Saturday’s running in order to make an early departure to their hotel before nightfall.
Four of the team’s mechanics had been caught up in a confrontation between police and protesters on the highway back to the capital city Manama on Wednesday evening when a petrol bomb exploded close to their unbranded rental car.
Two members of the Silverstone-based team reacted to the incident by asking to leave and they flew home on Thursday.
The Sauber team on Friday also issued a statement that confirmed they drove through a similar incident on Thursday.