This arrow roller is made in house and to the design I use myself. It is designed to use only with wooden arrows. You simply identify where the bend in the arrow shaft is and then apply pressure whilst rolling over the high part of the bend. What this is doing is crushing the fibres of the shaft. Whilst this sounds brutal and you would imagine it impacts the performance and properties of a shaft, I have never noticed any change in performance of an arrow however many times I have straightened it.
That said, when I make my custom arrows for customers I ensure the shaft is perfectly straight prior to measuring the spine!
The roller is made to last. It's main body will be made of a hardwood, often bubingha or wenge, and the roller is made of nylon with a captive bearing so it rolls super smooth. The round groove in the roller ensures pressure is applied around the arrow shaft. The roller fits both 5/16ths and 11/32nd shafts.
Since the vast majority of wooden shafts don't arrive straight and don't stay straight for long if shot in woodland it's essential for any archer looking to shoot woodies in a half serious way to have the know-how and tools to straighten them out.