As Fernando Alonso exited the Ferrari garage to set off on his first hot lap in the final 10-minute qualifying session, he almost ran into Rosberg who was heading down the pit lane in his Mercedes.
The German was forced to brake sharply to avoid colliding with the Spaniard, following which he issued an immediate retort over the team radio as he snapped: "Alonso should get a penalty for that."
After swiftly reviewing the matter, the four stewards deemed the maneuver an unsafe release from the pits, and in accordance with the regulations, fined Ferrari US dollars 20,000 (Â£13,500).
Explaining the issue, Rosberg said: "There were some photographers standing there, who I've just spoken to now.
"For them, if we had collided – and it was very possible to collide in that situation – parts could have started flying and it would have been very dangerous for them.
"So it's a serious thing and I think it's correct they (Ferrari) got a fine.
"They really need to try and do better next time. That was not good."
05/08/10 (GMM) Stewards fined Ferrari $20,000 after investigating the pitlane incident during qualifying involving Fernando Alonso and Nico Rosberg.
The pair almost collided in Q3 when Ferrari's Alonso exited the garage into the path of Mercedes' Rosberg, who had to take avoiding action and nearly struck the pitwall.
A stewards' statement confirmed that the Maranello team was guilty of an "unsafe release", and referred to the rule requiring "all pitlane and track and safety measures to apply to all practice sessions as for the race".
05/08/10 (GMM) FIA officials in Spain have confirmed reports the stewards are investigating the pitlane incident during qualifying involving Fernando Alonso and Nico Rosberg.
The pair almost collided when Ferrari's Alonso exited the garage into the path of Mercedes' Rosberg, who had to take avoiding action and nearly struck the pitwall.
Engineers on the Williams pitwall flinched at the near-crash, and Rosberg said on the radio that he thinks the Spaniard should be penalized.
Lewis Hamilton and Sebastian Vettel were reprimanded for their pitlane stoush three weeks ago in China, although it is believed the FIA's Charlie Whiting further admonished Vettel's moves when the drivers met for their pre-race briefing in Spain.
Alonso said in Barcelona: "Hopefully they (the stewards) take into consideration there was no accident, no touch, no performance gain from the move."