Well, once the orientation of the eggs is set, they should not be rolled. The eggs need to develop with the yolk down and the embryo up. However the orientation isn't usually 'set' until sometime after they've been laid (usually within 24 hours is the most commonly accepted time frame) however this can be quite variable. This is why it is important to candle your eggs. I have a female who usually lays 8 or 9 eggs, but every year half of them would die. I finally picked up a flashlight powerful enough to see the embryo inside the egg and I noticed that half of her eggs had the orientation upside down as they were laid, I was able to cut them apart from the clump and now they all hatch