Aside from other differences, I think a rolled thread would leave the threads slightly proud of the rest of the steerer tube. (Measure the diameter of a spoke on the shaft and at the threads to see what I mean.) That would require a slightly different inside diameter of the upper cup for the headset to fit.

All the threaded fork steerers I've worked on have had cut threads, and, BITD, we would cut a few more threads on a replacement fork if we didn't have one that fit.