The rolling technique is where you press the base of your tweezers into the base of the lashes and roll gently from side to side. As you roll along the base each lash will rotate and splay outwards to make your fan.
How to make the fan
Isolate the number of lashes you would like
Pick up and place back onto the strip
Use your tweezers to press into the very base of the lashes
Roll your tweezers back and forth to open your fan
Grip tightly, pull forward and off of the strip
If you find that your lash strip does not have enough tack to hold the lashes in place while you roll, use the variation of this technique where the base of your lashes is not taken from the strip but pulled to the side instead.