I think this should be done with lube (or maybe flour :) ). Think of rolling dough. The rolling pin stretches the dough as it flattens. You need some way of allowing the ventral side of the penis to slide forward during the motion.
For safety, I would consider constructing a flexible rolling pin. It will slightly arc when force is applied to the handles, relieving some pressure from the dorsal veins and nerve and increasing it on the CCs. It will also add some compliance to the system. The problem with a wooden rolling pin on a table is that the penis is literally between a rock and a hard place. This leaves no margin for error and greatly increases the likelihood of injury. I have no ideas at the moment for how to make a flexible rolling pin, but it’s probably not hard (no pun initially intended).
Because you can realistically roll out the dorsal side of the penis only, I would expect that the rolling pin technique preferentially stretches the dorsal side of the tunica. Take this with a grain of salt, but that suggests to me that this technique may tend to induce a downward curve. Using lube might tend to reduce this effect.
I started doing that exercise a couple of months ago, standing on my knees I used a big role, the ones you use in the kitchen and applied pressure to my unit constantly and slowly.
It’s really effective, so give it a try. I haven’t measured yet but still I see the progress in my hands.