Preheat the oven to 200°C, fan 180°C, gas 6. Place the garlic and all the veg in a large roasting tin (big enough so that the vegetables are in a single layer). Pour over the olive oil and toss together. Roast on a high shelf in the oven for 20-25 mins until golden and tender. Remove from the oven and toss in the basil leaves.
Blitz 4 tbsp of the roasted vegetables in a food processor until fairly smooth. Stir the purée back into the remaining roasted vegetables in the roasting tin.
Spoon a few tablespoons of the roasted vegetable mixture into the bottom of a 2 litre ovenproof dish. Place a layer of lasagne sheets on top then another layer of the roasted vegetable mixture. Continue with another layer, finishing with lasagne sheets to cover the top.
Tip the crème fraîche into a bowl and add 3 tbsp water, stirring until smooth. Spoon over the top of the lasagne then sprinkle with the parmesan and mozzarella. Bake for 20 mins until golden and bubbling.
To cool, cover the cooled lasagne with cling film, then foil, and freeze for up to 3 months. Defrost completely (overnight in the fridge is best) before baking for 25-30 mins at 200°C, fan 180°C, gas 6.