Kimi Raikkonen believes Lotus has the pace to match the single-lap speed of rival Mercedes in Monaco following the first two practice sessions on Thursday.
Rosberg, who has started from pole in the last two grands prix, was the only man to lap in the 1m14s in the second session.
Raikkonen, however, sees no reason why Lotus cannot match Mercedes' pace in qualifying, although the Finn is refusing to make predictions.
"I think yes, if we get all the things right," Raikkonen said when asked by AUTOSPORT if Mercedes' lap time was within reach.
"We will see. Why not? We see what happens on Saturday.
"You would think they will be very fast. Today they were very fast, but things can change. We have to wait and see. I have no interest to start guessing what can happen on Saturday."
He added: "We have to see how it is in the morning. If it's like this morning then it's going to be a disaster. But we improved a lot and it's getting better and better all the time.
The Lotus driver said starting from the two first rows of the grid will be crucial if he wants to have a shot at winning the race.
"If we want to win, probably yes," he said.
GROSJEAN CONFIDENT DESPITE CRASH
Team-mate Romain Grosjean finished his day early after crashing against the barriers at Sainte Devote in the second session.
The Frenchman managed just 10 laps, but is confident the accident will not affect his performance this weekend.
"It is not a big deal. It's a bit of a shame, as we lost some time, but the confidence is there," he said.
"I locked when I was already into the corner so unfortunately there was nothing I could really do.
"I think it's going to be tight. Fernando [Alonso] is quick, both Mercedes are, and I think we are, so it's going to be a good battle."