Grate the potatoes and squeeze out the excess water using your hands or a clean towel.
In a bowl, mix the grated potatoes with mozzarella cheese, parsley, egg, salt, and black pepper until combined.
Line a baking sheet with parchment paper. Spread the potato mixture evenly on the parchment paper, smoothing it with a spatula
Bake at 180°C (360°F) for about 20-25 minutes, or until golden and firm. Set aside to cool slightly.
Heat olive oil in a skillet over medium heat. Cook the ground beef until browned. Add the onion, green bell pepper, and red bell pepper, cooking until softened (5-7 minutes).
Stir in tomato paste and mix well. Add water, salt, paprika, and black pepper. Let the mixture simmer until the liquid reduces and the filling thickens (about 10 minutes).
Spread the meat filling evenly over the baked potato layer. Use the parchment paper to roll the potato layer into a log, keeping it tight.
Sprinkle mozzarella cheese on top of the roll. Return it to the oven and bake at 180°C (360°F) until the cheese melts and is golden (10-15 minutes).
Slice the roll into pieces. Serve warm and enjoy!
