Kimi Raikkonen enjoyed a more productive morning in his Ferrari and ended second fastest.
Mercedes trialed a 'megaphone' exhaust on Rosberg's W05 Hybrid during the first couple of hours of running but this did not have any effect on the noise levels. The German headed into lunch third quickest.
Esteban Gutierrez conducted the majority of his running during the initial stages of the session as he brought his Sauber back to the pits with a few flames trickling from the rear of the C33.
Jules Bianchi assumed testing duties following Max Chilton's strong pace on Tuesday and ended the morning fifth fastest.
Sebastian Vettel only appeared during the final hour as Red Bull worked on the RB10 after gearbox issues hit the car on Tuesday.
Susie Wolff sampled the Williams FW36 for the first time in anticipation of her practice appearance at the British and German Grands Prix. She spun off at Turn 11 on her sixth lap of the track.
McLaren young driver Stoffel Vandoorne made his Formula 1 testing debut and the GP2 race winner conducted tire testing for Pirelli, as did Force India reserve Daniel Juncadella, whose car ended up in the gravel on the exit of Turn 4.
Daniil Kvyat took over testing duties from team-mate Jean-Eric Vergne but completed only five laps before his STR9 ground to a halt at turn three. He returned to the circuit again but stopped on his first lap.
Caterham did not run Robin Frijns due to the damage sustained to the CT03 following Kamui Kobayashi's crash on Tuesday.
|7||Sebastian Vettel||Red Bull||1:27.973||73|
|8||Daniel Juncadella||Force India||1:28.278||91|
|10||Daniil Kvyat||Toro Rosso||1:28.910||21|