Tall Paul, what size P-38 was that one? I had a 56" wingspan P-38 that flew awesome with two os 25. Had one engine flame outs a few times and always landed safely. The plans called for 3 degrees of outward thrust on each engine to compensate for a one engine out situation. I also had an old cessna 310 but the plans didnt call for the outward thrust but thank god I used it. Seems your friend's P-38 wasnt built with that offset thrust and what you said is exactly what happened. The original P-38 had opposite turning propellers spining in a direction to overcome the rolling motion created by the prop torque during one engine out. I actually saw a small twin Stick with 049s that did exactly what your friends airplane did when one engine died. After inspection one one engine was straight and the other one had inward thrust. To honor murphys law.....the one who remain running was the one with inward thrust and................well the twin stick had a lot of sticks laying around.

But to answer Bryans question, assuming both engines are running properly you should experience very little difference when the airplane rolls on each direction.