Buy a standard wrist roller if you want, but a homemade version of PVC pipe (1.5 to 2 inches is perfect) with climbing webbing attached is a cheap and amazing solution.
Check our power-rack version that we made out of aluminum tubing. The beauty of it in a rack is that you can truly test the grip without the shoulders giving out first.
The purpose of this column is tri-fold. Purpose number one is as a "refresher course" for seasoned lifters. Sure, deep down, you may know this stuff, but it's been so long since you first read about it that you've forgotten the rationale behind the subject matter.