Greedy,
b1nzen48 set me straight on that: the rollers aren’t supposed to roll. The metal end pieces that go in either side of the rollers are square so the rollers aren’t able to rotate. It’s a good thing. That way the rollers grab you way down the shaft and sort of duplicate what your hand does when you dry jelq. (As has been noted earlier, you still don’t get the sides of your cock unless you turn the device sideways.)
And that link I provided is just one source for a canning jar lifter/power jelq device. Search for “canning jar lifter” and you’ll see a ton, or, if you have a decent gourmet cooking store near you, you can probably buy some tongs tomorrow for less than six or seven dollars.
One thing about the self-adhesing armacell foam for the rollers: cut it so it’s slightly wider than the width of the rollers — ideally the distance from one metal holder to the other. That allows you a wider space to jelq in, and permits a little sloppiness if you get distracted for some reason.