Spring Verde Lasagna

Name: Spring Verde Lasagna
Ingredients: 2 tablespoons butter, unsalted; 3 tablespoons flour, rice or all-purpose; 1 teaspoon salt; 2 cups milk; 1 lb spinach, or other dark leafy greens; 1 lb ricotta cheese; 1 cup peas, fresh or frozen; 1 cup artichoke heart, fresh or frozen; 2 cloves garlic, finely minced; 1 package lasagna noodles, or gluten-free noodles; 1 tablespoon lemon-zest, optional; 2 tablespoons fresh herbs, such as basil, sage, mint, or parsley; 8 ounces fresh mozzarella, thinly sliced