On the back of a disappointing first two races to the campaign, Rosberg delivered his team's most competitive performance of the campaign to lead the race for 14 laps.
And although fuel consumption issues slowed him down and resulted in him dropping to fifth at the flag, Rosberg says the fact the team came close to such a strong result was good grounds to feel upbeat about future prospects.
"We are optimistic for one, which is nice," Rosberg told AUTOSPORT. "It is good to see after such a disastrous start, to turn it around and then lead the Shanghai race for I don't know how many laps. No one saw that coming and it was brilliant wasn't it? It was great stuff.
"There is a feeling of optimism again. But we are still one second off Red Bull Racing in qualifying, so we need to be careful because we need to be one tenth ahead of them."
Rosberg said him being able to lead the race was a surprise - and he was even more shocked when he was able to keep a comfortable margin at the front before his second stop for tyres.
"It was pace," he said. "I saw a Red Bull in my mirrors and it wasn't coming closer. It was staying the same size, and I thought, 'what is going on?'"
Rosberg believes the turnaround in form for Mercedes GP since last weekend's Malaysian GP was simply the result of the team extracting more speed from the car because the only major changes to the car were that it did not need to be compromised for the high levels of cooling that had been required in Sepang.
"We are just extracting the best from the car now," he said. "Set-up, basic things even, just coming together, understanding better an example is big chunks of time from basic springs and parts. So that is good. It is not everything, a small bit, but there are bits and pieces everywhere."
When asked if he felt a win would have been on the cards if he had not had to go into fuel saving mode, Rosberg said: "I don't know. I don't have the numbers, but I am going to believe in it. Why not?
"I don't have any numbers so I cannot back it up with facts, so I don't know if my belief is in anyway realistic, but that doesn't matter.
"We would have been second at least though, I guess. I don't know why I wouldn't have got Sebastian Vettel."
Rosberg had to save fuel in the race because Mercedes GP had made a miscalculation about its fuel consumption figures. The team's pace in the race was much faster than it had predicted, and that meant the German was burning more fuel than had been expected.