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.
Most people think the bench press builds the best pecs. Well, most people are wrong. The dip is better. And it can be a great triceps exercise as well, if you do it right.