Preheat oven to lowest temperature, 170 degrees F (that was the lowest setting on my oven). Line 2 or 3 12x18 inch jelly roll pans with parchment paper, good-quality plastic wrap or silicon baking mats (I have tried all 3, the baking mats are BY FAR the easiest to prep and peel).
Combine ingredients in a blender or food processor and process until smooth. If desired, strain liquid through a mesh strainer into a clean bowl (this is not necessary, but if you or your kiddos prefer your fruit roll ups without seeds, this step is recommended). Discard solids.
Divide mixture between your prepared baking sheets, using an offset spatula to create a very thin, equal layer. I found that tapping the side of the pan against the counter helped in equally spreading the pureed fruit.
Bake for 4-6 hours, checking periodically. Rotate pan every 1-2 hours for more even cooking. Your fruit roll ups are done when the puree is dry to the touch and pliable (note: the exterior part of the fruit roll ups may dry sooner than the middle).
When finished baking, remove from oven, peel off parchment or mat and gently transfer to a cutting boards. Slice into desired sized, roll with parchment paper or wax paper and store in an air-tight container for up to one week.