What is palm rolling?
Palm rolling is a method for compressing knots that have dread wax in them and helping them tighten. It works much better than "twisting" around and around. To palm roll you simply grab the dread between the base of your palms and rub it back and forth with squeezing pressure. It's a bit like rolling Play-Doh between your palms to make it long and skinny.
The dread wax in the center of the dread will allow the hair to move so the knots can tighten when they are squeezed and rolled by the palms. Everything about how DreadHead Dread Wax aids the compression and tightening to help the dread mature faster is explained here.