Despite starting on pole, the the German endured a frustrating afternoon as he slipped to a ninth-placed finish in the fourth race of the season.
Afterwards the 27-year-old conceded that he did not feel at his best during the race.
"As nice as it was to start from pole this afternoon, it was just as hard to finish in ninth place," Rosberg told BBC Sport.
"I didn't feel comfortable in the car today and it wasn't much fun out there really."
Rosberg sits ninth in the drivers' standings.