Lewis Hamilton ended the session in second and just 0.057s behind his team mate. The Briton had been top at the halfway stage, but didn't improve on his second run and was consequently jumped by Rosberg, who has previous form at the circuit after claiming pole and victory last time out in 2014.
Sebastian Vettel backed up team mate Raikkonen's pace meanwhile by securing fifth, two tenths down the road from the Finn, while Max Verstappen in the second Red Bull also got within half a second of Rosberg's benchmark - suggesting qualifying could be a much closer affair than the timesheets on Friday indicated.
Williams jumped up the order, with Valtteri Bottas heading Felipe Massa for seventh, while McLaren's Fernando Alonso and Force India's Nico Hulkenberg rounded out the top 10.
It was Rosberg who gained the ascendancy early on, topping the timesheets with 1m 16.134s on the supersoft Pirellis. Hamilton's first flyer lifted him above his team mate and title rival, and the Briton then trimmed that to 1m 15.795s - only to see Rosberg do 1m 15.738s to effectively secure top spot.
There was bad news of a different nature for Hamilton too - he and Mercedes are currently being investigated for an unsafe release into Romain Grosjean's path early in the session.
The French driver had to slow to avoid an accident - which was just the first in a series of mishaps for the Haas man, who also suffered a half-spin exiting Turn 4 and was restricted to just four laps in total as gearbox issues struck. Haas spent the final part of the session replacing the gearbox with a new unit, which means Grosjean now faces the threat of a grid penalty for Sunday.
Ricciardo also spent much of the session in the garage, although in his case it was apparently be design rather than misfortune. When he did emerge, he gave Red Bull reason to be optimistic as he produced a 1m 15.837s late on, carrying him to within 0.1s of the top. Raikkonen’s 1m 15.902s showed that Ferrari could also be a threat in qualifying.
Elsewhere, Sergio Perez damaged the front of his Force India running wide in Turn 1, while Jenson Button - fully recovered from his eye trouble yesterday - could only manage 19th, complaining of both understeer and oversteer on his McLaren.