Pesto Lasagna Rolls

Bahan-bahan (6 porsi)

• kosher salt
• 12 whole lasagna noodles
• 2 tablespoons unsalted butter
• 2 tablespoons all purpose flour
• 1½ cups whole milk
• freshly ground black pepper
• 1 large egg
• 2 cups ricotta cheese ((we prefer whole milk))
• 10 ounces frozen chopped spinach, (thawed and squeezed dry)
• 2½ cups shredded mozzarella cheese, (divided)
• ¾ cup grated Parmesan cheese, (divided)
• 1 cup store-bought pesto sauce, (divided)
• crushed red pepper flakes, (optional)