- Pre-heat the oven to 200 deg. C., 400 deg. F., Gas Mark 6.
- Put the onion, pepper, courgette and butternut squash into a large roasting tin and add the olive oil. Season and toss to coat. Roast for 15 minutes in the pre-heated oven, then add the chorizo. Roast for 10 more minutes, until the vegetables are tender.
- Add the cherry tomatoes and pasta sauce to the roasted vegetables. Transfer half the mixture into a large rectangular baking dish, measuring about 25 x 20 cm (10 x 8 in). Arrange 3 lasagne sheets on top of the mixture. Repeat the layers.
- To make the cheese sauce, put the milk, butter and flour into a non-stick saucepan. Heat, stirring constantly with a small whisk, until the sauce boils and thickens. Add two-thirds of the cheese, stirring until melted.
- Pour the sauce evenly over the top of the lasagne and sprinkle the remaining cheese on top. Bake in the oven for 30 to 35 minutes, until golden brown.