Trust me on this I've tried it, not as good as good for the forearms as the wrist roller in my experience. I'm not going to argue but I want you to try this, however much weight you're doing in a kickback, try doing that with the the wrist rolls. That'd be enough that Popeye would be bleading from his anchor.

I didn't include the other weight training exercises I don't see it as necessary for a boxer. You could say that doing deadlifts helps your lowerback and your forearms, but it's not going to do make much of an impact on your boxing. There are more constructive ways to build strength, Scrap has a few nifty ones here that are more suited for a fighter.