Hearty Sweet Potato Lasagna

Name: Hearty Sweet Potato Lasagna
Ingredients: 2 pounds sweet potatoes (about 3 large); 1 large yellow onion; 3 cloves garlic; 2 large sprigs fresh oregano, divided; 1/4 cup olive oil, divided, plus more for the pan; 8 ounces ground beef (preferably 85% lean); 8 ounces uncooked sweet or hot Italian sausage, casings removed if using links; 2 teaspoons kosher salt, divided; 1 teaspoon freshly ground black pepper, divided; 3 tablespoons tomato paste; 1 cup dry red wine; 1/4 cup Worcestershire sauce; 1 1/2 teaspoons Italian seasoning; 1/4 teaspoon red pepper flakes (optional); 1 (28-ounce) can crushed tomatoes; 1 1/2 teaspoons granulated sugar; 1 small lemon; 1 large sprig fresh basil; 2 large eggs; 1 (15- to 16-ounce) container whole-milk ricotta cheese; 5 ounces Parmesan (about 1 1/4 cups firmly packed grated on a Microplane), divided; 16 ounces low-moisture, whole-milk mozzarella cheese, shredded (4 cups)