Combine the ketchup and jam and mix together in a small bowl; set aside.
Thinly slice a sweet potatoe using a mandolin (1.5 mm slices).
On a baking sheet, lay out a piece of foil. Place a single layer of sweet potato pieces on top.
Sprinkle with salt and dried rosemary evenly over the slices.
Place in the oven; bake for 10-15 minutes, checking often to make sure the slices do not get too toasty (unless you like them toasty like our family does).
Turn off the oven. Leave sweet potatoes in the oven; door open. Remove when you are ready to serve (warm) with Marion Blackberry dipping sauce.