Pre-heat oven to 180 °C with top and bottom heating.
Wash the eggplant and zucchini and cut into slices. Peel and dice the onions and garlic and sauté in hot oil until transparent. Add the eggplant and zucchini and sauté all together for about 6-8 min. Season with salt. Add the chopped tomatoes and season with salt and pepper.
To make the sauce, melt the butter in a pot. Add the flour, let sweat briefly. Slowly pour in the milk little by little while stirring and stir until smooth. Bring to a boil and season with salt, pepper and freshly grated nutmeg.
Drain and slice the Zottarella Roll. Pour some of the sauce into a casserole dish. Place three lasagne sheets inside, layer with vegetables, Zottarella slices and sauce. Then place three more lasagne sheets and layer again with vegetables, Zottarella slices and sauce. Repeat the layering again and finish with a sauce layer. Sprinkle with grated cheese and bake in the oven for about 35-40 min.