Mercedes had been a popular tip for victory heading into the weekend, and Rosberg proved such views were not without foundation as he went fastest in both practice sessions in the Principality.
Rosberg feels Mercedes can be confident it is at least in the hunt for what would be a fourth straight pole position, but admitted there is still uncertainty over the opposition's pace.
"Generally I'm pleased with today, it was a good day going in the right direction," Rosberg said.
"I felt comfortable in the car, and we know we're more or less in the hunt for a good result in qualifying - somewhere towards the front – but we have to wait and see.
"We really don't know what other teams are doing, what they are running.
"I don't know if [Mercedes' pace] is going to be enough or not.
"The other thing is long-run pace: it's better, but there are still some issues there, it still could be a problem. So there are a couple of question marks."
Asked whether Mercedes could carry its practice two form into qualifying and secure another front-row lockout, Rosberg added: "It's way too early to think about that."
Hamilton, who progressed from fifth to second fastest over the opening two sessions, admits he still needs to find time from himself and through the car.
The Briton, outqualified by Rosberg in Bahrain and Spain, trailed his team-mate by three tenths of a second in the second session.
"It looks pretty good, I just have to improve my one-lap pace – there's a bit from me and a bit from the car," Hamilton explained.
"We had a bit of graining and understeer, but the long runs seemed to go pretty well, so we'll see."
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