Start by preheating your oven to 400°F. Line a 17” x 12” baking sheet with parchment paper and spread an even layer of shredded mozzarella cheese on it. Next, slice your peeled potatoes using a mandoline into 1/8-inch-thick pieces. Layer the potato slices on the baking sheet, slightly overlapping them. Brush with olive oil and sprinkle with salt, paprika, and onion powder. Bake for 20-25 minutes until the potatoes are tender.
While the potatoes bake, heat olive oil in a large pan. Sauté chopped onion, green bell pepper, and red bell pepper for about 3-4 minutes. Stir in minced garlic and cook for another 30 seconds. Add the ground lamb and break it into small pieces with a wooden spoon until fully cooked. Drain any excess fat and stir in tomato paste, marinara sauce, and seasonings. Cook for an additional few minutes and set aside.
Once the potato layer is slightly cooled and manageable, sprinkle on a little more mozzarella cheese. Spread the filling evenly over the potatoes, taking care not to disturb the layers underneath. Sprinkle more cheese on top. Starting with the shorter side of the rectangle, roll the potatoes tightly into a log. Carefully transfer it to the baking sheet with the seam side down.
Top the roll with a final sprinkling of shredded mozzarella and bake for another 7-10 minutes until golden and bubbly. If the roll begins to separate, use spatulas to gently press the sides together.
Allow the scalloped potato roll to rest for 5 minutes before slicing it into thick rounds. Enjoy the crispy, cheesy, and savory results!