Roll Clipping is a technique which allows you to roll through some walls from climbing up a ledge. Roll Clipping is done by being partway inside of a wall while hanging on a ledge. After climbing up the ledge, there is a single frame in which you must roll towards to wall. If you were far enough inside of it, rolled at the correct angle, and rolled on the correct frame, you will roll through the wall.
In the original Wind Waker, you will always roll into the wall without jumping. This makes some skips require more leaf pumping in order to keep the necessary height.
Note that in Wind Waker HD, you will immediately jump when performing a Roll Clip. This can be convenient for gaining extra height for some skips, but also makes other skips more difficult because Link will jump out of the wall and go back in bounds. In order to prevent yourself from jumping, let go of the control stick as song as you roll.
On ledges that would not normally allow you to roll clip or ledges where you need more height than what a normal ledge clip would provide, a Bomb Roll Clip can be used. In order to perform a Bomb Roll Clip, perform a ledge clip but place the bomb a bit further away from the wall so that you only clip partially into the wall. After doing so, climb up and perform a roll clip in order to fully clip out of bounds. The video below demonstrates a Bomb Roll Clip.