I am not sure but I remember it as FF...
You're both right! In the game, Spirit tells you it was a Heat Seeker but in the Strategy Guide Maniac claims it was a Friend-or-Foe.
Maniac was the one who killed Rosie, accidently, of course.
I think Rosie was the one who killed Rosie -- she disobeyed orders... to impress the guy she liked. *She* was the hardened veteran who should have known better -- Maniac was flying his second combat mission even (third counting the training flight that turned into a battle against a blockade runner on Academy...).
Although it's not confirmed as his fault, [Vagabond] died after playing cards with Maniac.
It's not even implied to be his fault. His 'dead man's hand' in the poker game is just a signifier that he's going to die -- not that the person who beat him is going to kill him somehow.
And Catscratch was taking Maniac's advice, leading to his death.
But according to Star*Soldier, Catscratch is still alive thirty years later... and reviewing Maniac's book.
And don't forget that the Wild Eagles from SO2 were trained to fly just like him and most of them died too!
None of the Wild Eagles died flying, though. One was killed (and one crippled) when the Concordia's flight deck was bombed and the third died of radiation poisoning after Blair destroyed Ayer's Rock.
But there were those two pilots in Prophecy who died on his wing because he couldn't help them.
Their names were Vanguard and Cantrell, IIRC.
Losing your wingman is not at all the same thing as killing your wingman -- and you only know that this happened in the first place because of a cutscene in which Casey tells Maniac that "you did the best you could to help those rookies survive. Which is all a good squadron commander can ever do".
But yes, there is the transport crew that he accidentally killed.
... which, all in all, balances fairly well against his 2,000 air-to-air victories against the enemy (*before* Prophecy!).