The German lapped the 5.4 kilometer Sakhir circuit in one minute 32.330, two-tenths of a second faster than Vettel with Alonso less than a tenth off Vettel’s time in third.
Rosberg’s pole position in Bahrain comes just a week after teammate Lewis Hamilton topped qualifying for the last race in China and underlines the improvement the Brackley-based squad has made after enduring three largely unsuccessful years since Mercedes returned to the sport as a manufacturer.
However, racing in the desert heat will be a whole different matter and it’s the cars which look after their tyres the best that will come out on top over the 57-lap race, an area where Mercedes are still lacking compared to their rivals.
Ferrari have been quick in race trim so far this year and once again showed promising long run pace in Friday’s practice sessions. A good start from third could set Alonso up for his second win on the trot.
Behind the top three, Lewis Hamilton qualified the second Mercedes in fourth. But the Briton will start the race ninth as he takes a five place grid penalty due to Mercedes fitting a new gearbox to his car following the third practice session.
Mark Webber set the fifth fastest time but will also drop down the grid as a result of a three-place penalty the Red Bull driver carries over from the Chinese GP. He will start the race seventh after accounting for Hamilton’s drop.
The penalties for Webber and Hamilton mean Felipe Massa will start alongside his team-mate in fourth. The Brazilian qualified on the hard compound tyres, an indication that he could be planning to run a long first stint.
Force Indias impress
The two Force Indias were back on form and will start behind Massa from the third row of the grid after accounting for Webber and Hamilton’s penalties, with Paul di Resta just pipping teammate Adrian Sutil to set the seventh-fastest time.
Mumbai Roundup: 9 incidents that took place this week
Photos: Ajay Devgn, Parineeti, Tabu at 'Golmaal Again' trailer launch
Photos: Dipika Pallikal Karthik oozes oomph in bikinis and sarees
Photos: Kareena Kapoor Khan's grand birthday bash
Photos: 'Dangal' girls Sanya Malhotra, Fatima Sana Shaikh's dinner outing