Lewis Hamilton took a massive step toward ending his team-mate's Monaco run as he claimed pole position for the prestigious race.
With dark clouds overhead, Hamilton and Rosberg were immediately out at the start of Q3.
Using the red-marked supersoft tyres, Hamilton led his team-mate out of the pits and put in a banker lap of 1:15.304. Rosberg's was 0.136s slower.
The Brit was again the first of the Mercedes protagonists out on track for a second attempt at pole position. However, like many of his rivals, Hamilton was visibly struggling to get heat into his tyres.
Despite that, he posted a 1:15.098 to secure his first pole position ever at the Monte Carlo street circuit. Rosberg did not even complete his lap, opting instead to pit after making a mistake.
As such he finished 0.342s behind his team-mate in yet another Mercedes 1-2. Saturday's pole position was Hamilton's first in Monaco.
Sebastian Vettel's time from his first run, a 1:15.849, meant he finished third ahead of the Red Bull of Daniel Ricciardo.
Daniil Kvyat was P5 in Red Bull's best qualifying showing of this season while Kimi Raikkonen could only manage sixth. The Finn, who crashed in FP3, revealed he had a brush with the wall at Portier on his first run.
Sergio Perez was seventh ahead of Carlos Sainz, Pastor Maldonado and Max Verstappen.
Fernando Alonso's qualifying ended in Q2 when MP4-30 shut down on him, forcing to him to grind to a halt at Ste Devote while down in 15th place.
But the big shock of qualifying came in Q1 when Valtteri Bottas failed to progress.
The Williams driver was one of the last to put in his final lap, down in the dropzone as he began it. However, he just did not have the pace needed to improve and qualified P17.
01 Lewis Hamilton Mercedes 1:15.098
02 Nico Rosberg Mercedes 1:15.440 0.342
03 Sebastian Vettel Ferrari 1:15.849 0.751
04 Daniel Ricciardo Red Bull 1:16.041 0.943
05 Daniil Kvyat Red Bull 1:16.182 1.084
06 Kimi Raikkonen Ferrari 1:16.427 1.329
07 Sergio Perez Force India 1:16.808 1.710
08 Carlos Sainz Toro Rosso 1:16.931 1.833
09 Pastor Maldonado Lotus 1:16.946 1.848
10 Max Verstappen Toro Rosso 1:16.957 1.8
11 Romain Grosjean Lotus 1:17.007
12 Jenson Button McLaren 1:17.093
13 Nico Hulkenberg Force India 1:17.193
14 Felipe Massa Williams 1:17.278
15 Fernando Alonso McLaren 1:26.632
16 Felipe Nasr Sauber 1:18.101
17 Valtteri Bottas Williams 1:18.434
18 Marcus Ericsson Sauber 1:18.513
19 Will Stevens Manor 1:20.655
20 Roberto Merhi Manor 1:20.904