Hey Dan:
I apologize for the delay. I have neglected to check this forum since the last time I checked this forum. :-) . I am now making the commitment that as long as I am in town, I will check at least twice a day, once in the morning after I awaken; and, again at night before heading for the bed. If I go on a trip, I will be sure to let people know how long I will be gone prior to my trip.
Thanks so much for your question�
There are three distinct phases as a bowling ball makes its way down the lane after you release it from your hand - skid, roll, and hook. Regardless of any factors, these three phases will occur.
So, for your question, the "roll" is that in-between phase when the ball comes out of its initial skid, enters into its forward rolling motion and continues down the lane until it hits the breakpoint, at which time it begins its hook toward the pins.
The length of time the ball remains in each of these phases depends on hand position at time of release, speed of delivery, how much oil is on the lane, the pattern that is laid down on the lane, and where the weights are placed in your ball when drilled.
A Hui Hou,