Infield flyball is hit (infield fly rule not in play), defense does not catch it, batter makes it to first before it roles out of in field. Batter is safe at first, no foul ball, right???
Depends on where it rolls out. Did it pass 1st or third before it rollled out? Fair ball. Did it not pass either base? Foul ball. How far the runner went doesn’t matter
Did the defense touch the ball in fair territory? Did the ball pass first base or third base before going foul? If either of these is yes, than fair ball.
Otherwise as Chinamigarden points out if the ball rolled foul before passing 1st or 3rd base and not touched by the defense, then ball is foul even if the player was fast enough to run around all 4 bases before it crosses the line.