The German driver finished ahead of Lewis Hamilton to give Mercedes front-row seats at the Circuit de Catalunya, with both drivers still seeking their first wins of the season in a car which has plenty of pace but has lacked durability over the first four races.
Three weeks ago, Rosberg took pole in Bahrain only to finish ninth, and he is determined not to fall short again.
"We know that this is only half of the job completed and have the painful memory of what happened in Bahrain to prove that," said Rosberg, who is chasing his first podium this season. "We've worked very hard on our race pace but this track is tough for the tires, particularly with graining. It will be a big challenge tomorrow and our goal is to make the most of the opportunity from starting at the front."
While Hamilton had the fastest times in the first two qualifying sessions, Rosberg edged him to win the pole position in 1 minute, 20.718 seconds. Three-time defending champion Sebastian Vettel was third quickest.
"It will be a big challenge with the tires tomorrow," said Rosberg, whose best result this season was fourth at the Malaysian GP. "The race is very long and to win it's not good enough to start from pole — you still have to have the fastest race car."
Hamilton, the 2008 Formula One champion, is unsure how much to read into his team's qualifying speed.
"I've not been totally happy with the balance of my car all weekend, even today, so we need to look at it this evening and see what we can do for the race," the British driver said. "Limiting the degradation is going to be my major challenge as the general pace isn't too bad."
Vettel was satisfied enough with his performance as he finished ahead of Kimi Raikkonen's Lotus.
"I'm quite happy to be honest because yesterday and this morning I wasn't really happy. We improved the car and things calmed down," said Vettel, who has 38 career poles but none in Barcelona. "It's a tough challenge and the tires don't last as well as we would like."
The degradation of the Pirelli tires has been an issue all season, and drivers are largely unhappy about how quickly they wear out.
Ferrari has yet to secure a pole position this season, and it proved to be another frustrating afternoon for the Italian team after fast practice times in the morning. Fernando Alonso will start fifth and Felipe Massa ninth.
Massa finished sixth in qualifying but was bumped down three places for blocking Red Bull's Mark Webber on turns 11 and 12.
Jenson Button failed to make the cut for the third session. The Briton will start in 14th place, with teammate Sergio Perez in eighth.
"We've had a difficult couple of days. I had problems throughout practice, so to get through to Q3 was a great result, and something we really weren't expecting," Perez said. "I'm very pleased because I got absolutely everything out of the car."
Earlier, Massa was fastest in the third and final practice session ahead of Raikkonen.
Webber was third in final practice but had a poor qualifying session and will start from seventh place, behind Lotus' Romain Grosjean. They moved up a place due to Massa's grid penalty, as did Perez.
"I was disappointed with the lap in Q3 and lost a lot of time in the last sector," Webber said. "I'm normally quite strong there, but I was in trouble with the rears."
Ferrari wants its drivers to find extra speed in qualifying to increase the pressure on Red Bull. Once again, those hopes were unfulfilled.
The closest Ferrari has been to pole was when Massa qualified second in Malaysia. Alonso started the previous three races from third.
Mercedes has been fast but lacking durability this season, so Hamilton and Rosberg stayed on longer runs than other drivers in practice.
"It's going to be tough to keep these positions tomorrow," Hamilton said.
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