By this time, all the ingredients of your lasagna should be ready to assemble. Start by adding spoonfuls of your sauce to the bottom of a 9x13 baking dish (or a similar-sized deep baking dish) until it completley covers the bottom.
On top of the sauce, layer oven-ready lasagna noodles. Then, layer 1/3 of the ricotta mixture on top of the dry noodles. Next, arrange 1/3 of the roasted zucchini and eggplant in a single layer. Finally, sprinkle with 1/4 of shredded mozzarella.
Repeat by dolloping 1/3 of the sauce on top and spreading it. Add the second layer of dry lasagna noodles, ricotta mixture, roasted vegetables, and shredded mozzarella.
Repeat one more time: sauce, lasagna noodles, ricotta, vegetables, and shredded mozzarella.
Finally, pour the rest of the sauce on top of your layers and spread it evenly. Place the final lasagna noodles on top and sprinkle with the remaining shredded mozzarella. Grate Parmesan directly onto the top (about 1/4 cup).
Cover your lasagna tightly with aluminum foil and place it on a baking sheet. The aluminum foil helps it cook more evenly and prevents the sauce from spilling over. The baking sheet is there to catch any inevitable sauce spills.
Bake the lasagna in the oven at 400 degrees for 30 minutes with the aluminum foil on. Take off the aluminum foil at the 30-minute mark to melt the cheese and continue baking for an additional 15-20 minutes.
Take out your lasagna and allow it to cool (if you can help it) before serving.
This lasagna can be made a day ahead and stored in the fridge until you’re ready to pop it into the oven.