I've found the commercially available clay balls to be pretty accurate out to 20yds.
I too make my own, but only for something to do when out and about (I used to whittle sticks but kept cutting myself) and they are less accurate, but OK out to 10yds or so.
Yah, I used to make my own, but got lazy, the commercial ones are more accurate, so I just use them a lot anymore, they are pretty good out to around 20 yards or so, but crank them up to 250 fps, they get real strange, yeah I shoot them a lot, fun and cheap, Otherwise I shoot lead or steel
The local craft store had a 50% off sale on clay; so, I bought a couple packs and had a go at it last night. I paid ~ 5.50 for the 2 pound pack.
All in all, I happy with how the roller works. It does take a bit of practice to develop a technique. I think some of my troubles may be related to this air dry clay. I plan to make my own red clay as there is no shortage of it here in Georgia. I got a couple plates full out of the 2 pound pack. They're drying in the sun now, along with a new natty I made to shoot them. Once dry, I'll weigh them to determine a proper band set and the it's off to the races. The air dry clay takes 2-3 days to fully harden, so now it's just a waiting game. I really enjoyed making them. These are 20mm before drying; I'll also measure their diameter after drying. I forgot to mention above that I also bought a rolling table which is used to roll out the clay into a uniformed size for the boilie roller.