The whole point of rolling is under the left hook. As a southpaw I know when somebody misses their lead hook the easiest thing for me to land is my left hook, sure they are rolling away from it, but they aren't expecting it, especially if you go for the body, the left hook in that situation wouldn't get the same type of power behind it because the opponent would be in too close. It does look like he was tlaking about the left hook, but once again that is a stupid idea against somebody faster than you because, they are able to react with reflexes and won't jump into something stupidly, which Pacquiao didn't do.