In WW2, what is the magic number that had to be reached to be allowed home?

The number of missions that a bomber crew had to fly over Europe to be rotated out of combat duty during World War Two was 25.

Also, I think your information about who did it first is not accurate. I ran searches for Michael Roscovich, and found no references to him among any cite discussing airmen in World War Two. Second, the only reference to "Hell's Angels" and flying is that there was a Howard Hughes movie by that name done in 1937. However, it dealt with fliers in World War One, and had nothing to do with rotation home.

Also, the Memphis Belle and its crew achieved their notoriety precisely because they were the first to attain this lofty goal. Bomber duty, particularly in 1942 and 1943 was extremely risky because the B17 Flying Fortresses and the B24 Liberators had such long range that they could easily go far beyond the capacity of fighter planes to accompany them, so that in 1942 and 1943, the B17s often suffered losses at a rate of 25 percent or more, making survival through 25 missions an extraordinary feat. (Later in the war with the development of fighter planes that could accompany the big bombers on their entire 2,000 mile runs, the casualty rate dropped to only about seven percent.)

25.

25 combat missions and they could go home. Idk what it was raised to....probably 30.