Based on the builds I've done, I would say the trick is finding and maintaining the ideal bolt gap for your particular rifle/load. The half-moon "rollers" are obviously a way to help insure true, consistent lockup. But rollers that don't roll is as goofy as it sounds. The roller delay action is the biggest hurdle.
I've done accuracy builds with heavy and light barrels; with and without receiver enforcement; with regular and half-moon rollers. It didn't really matter, but Mike at TSC was very, very particular (as he is about everything) about the bolt lockup and maintaining it once he got it tuned right.
As time goes on, I'm beginning to believe that profile contour may be more critical than pure thickness until we get into heavy volume fire.
Just my $0.02