Agree with Dr Schwartz, rolling especially with 0.5 mm or more will cause too much collateral damage. Vertical delivery is best. Broken hairs are temporary and will grow back. The depth of the cells which generate hair is called the 'area of the bulge' and lies in the fat layer- way out of reach...
Because of their rolling action on the skin, I do not like rollers as they create a more erratic pattern of "tears" through the skin rather than the clean, more evenly distributed vertical punctures seen with the motorized micro-needling machines.
For the best results, micro-needling should be c...
