A jelly-roll pan looks similar to a cookie sheet, but it has four sides that are 1 inch high. Most jelly-roll pans are 10 1/2 by 15 1/2 inches or 12 by 18 inches, which is the size of a half-sheet cake pan.
The pan, which can be used as a substitute for a cookie sheet, is named after the rolled-up cakes known as jelly rolls. While traditionally used for baking, these pans also are appropriate to use for roasting vegetables or other foods that need to be spread out over a large, flat surface. The short sides of the pan contain any liquids that otherwise drip out while cooking.