Spread the diced potatoes evenly on a cookie sheet. Toss the potatoes with the olive oil and some salt and pepper. Roast the potatoes for 20-30 minutes, or until browned and cooked through. Remove them from oven and set aside.
Cook the pancetta in a small pan over medium heat until crispy. Remove from the pan and drain on paper towels. Evenly divide the herbs, cheese, spinach, potatoes, and pancetta for each tortilla – layer the ingredients, roll up, and place the rolled tortillas in a 9×13 baking dish.
In a medium bowl beat the eggs with the half & half and flour until smooth. Season the egg mixture with 1/2 teaspoon of salt. Pour the egg mixture over the tortillas. Cover with tin foil and keep in the fridge overnight. The next morning remove the enchiladas and let them sit on the counter for about 30 minutes before baking. Sprinkle additional shredded cheese over the top (optional).
Preheat the oven to 350°F and bake for 25 minutes covered. Remove the foil and bake another 5-10 minutes uncovered, or until the cheese is melted. Let the enchiladas rest a few minutes before serving.