ORIGINAL: NJRCFLYER2
The 45 line should be exactly bisected by the 1/2 roll. The judge should look for the beginning of the upright 45 line (at the end of the starting radius for the maneuver), then note the distance from there to where the roll occurs. To be really exact, it's the distance to the middle of the roll (at 90 deg)
This is not really correct. The criteria is for the line length before and after the roll elements, no matter what they are, to be the same. The roll element is independent of the lines before and after it. You are NOT centering the roll element itself, but rather you are making sure that the roll element segment is centered on the line by having lines before and after it that are exactly the same.
For instance, consider a 45 upline with an 8-point roll, opposite 1/2 snap roll. You DO NOT worry about where the center of that roll element is, all you do is make sure that the line before it and after it match exactly.