When creating your graphics, you want the finished file to be as wide as the circumference of your rolling pin and as tall as your rolling pin barrel.
As a quick geometry refresher – the diameter is how wide the barrel of the rolling pin is if you measured from the two widest outside points across the barrel. The circumference is the length if you wrapped a tape measure around the outside of the barrel. You can easily find the circumference if you take the diameter measurement and multiply it by 3.14.
Remember that if you are using text, the image needs to be reversed so that the text looks backwards. This ensures that the text is reading the correct way when it is embossed in the dough.