Rosberg ran wide at the chicane at the beginning of lap 29 and was forced to go down the escape road, allowing Hamilton to retake the lead after ceding it to his German counterpart at the start of the race.
That error came after Rosberg had survived the exact same mistake on lap eight at Monza and effectively ended his hopes of triumph as Hamilton was able to establish a relatively comfortable advantage.
And the world championship leader was quick to bemoan his loss of concentration on a day that saw his lead over Hamilton at the top of the standings cut to 22 points. "Lewis was just quick coming from behind so I needed to up my pace as a result and I just went into a mistake - it was very bad," Rosberg said.
"And that lost me the lead in the end, so it's definitely very disappointing from that point of view.
"Monza is one of the most difficult tracks for braking because of the low downforce and the highest speed of the year.
"It isn't an excuse, it is what it is.
"It is one of the challenges here and unfortunately I got it wrong two times in the race."
Despite the disappointment of throwing away the race win, Rosberg was keen to stress the positives from a frustrating day.
"Of course I am disappointed right afterwards, but it's still second, still a lot of points, so it is not a complete disaster," the 29-year-old added.
"I need to look at reality, there is worse than that - and I only lost seven points to Lewis."