I have been using this exercise that involves tying a weight to a bar. You roll the bar, holding it at chest level, until the weight makes its way up to the bar.

This burns my forearms, so I know it is working, but I don't think I am seeing very good results. I do it until I can't anymore, yet still I have only average forearms.

Is there something I am missing?

if you stand using pretty heavy dumbells, and face your palms away from you, with a tight grip, use your wrist to roll the weight up toward the ceiling, but try to not bend at the elbow at all ... i've noticed some results from that, you might, too ...

I may try this I have lots of spare wobble bits that need putting in its place...

I have managed to get hold of some weights through a friend who has 2 sets so that is nice of her

VERY! i hope it works out for you!