Always a crowd-pleaser, this lasagna is full of hearty veggies.
Preheat oven to 350°. Combine first 2 ingredients and 1 cup cream. Separately combine ricotta, next 2 ingredients, and 1 cup Parmesan. Sauté shallots in hot oil in a Dutch oven over medium-high heat 3 minutes. Add garlic; sauté 1 minute. Remove shallot mixture.
Add one-third of spinach to Dutch oven; cook over medium-high heat 1 minute or until wilted. Place spinach in a colander; drain. Repeat with remaining spinach.
Cook butter and flour in Dutch oven over medium heat, stirring constantly, 1 minute. Add 1 1/3 cups cream; bring to a boil. Remove from heat; add spinach and shallots.
Pour 1/2 cup sauce mixture in a 13- x 9-inch baking dish coated with cooking spray; top with 3 lasagna noodles. Layer half of spinach mixture, half of roasted peppers, 3 lasagna noodles, and half of ricotta mixture over pasta. Repeat layers; top with 3 lasagna noodles. Pour remaining sauce mixture over top. Place baking dish on a foil-lined baking sheet.
Bake at 350° for 1 hour. Top with 1 cup Parmesan, and bake 15 minutes. Let stand 30 minutes.