Veggie Gratin using up what's hanging out at home

So sometimes I'm a vegetarian, not always, I do like meat, for the most part, there exceptions, but sometimes the whole environmental impact of a meat based diet gets to me and I go off it. It's fine for the first few weeks, but eventually I'll start thinking about something meaty. Sometimes it means the end of vegetarianism, and sometimes it means creating a meat-free version. This was supposed to be meatless moussaka, but white sauce is actual work and ricotta based toppings are not, so, here we are, a great way of using up veggies. Sub out anything that does well precooked in oven.

Ingredients

1 eggplant, sliced thin
2 zucchinis, sliced
1 lb potatoes, peeled and sliced
Olive oil
Salt
Pepper

1 cup Tomato sauce
1/2 cup Shredded Gruyere cheese mix

Sauce

1 cup ricotta
1 cup milk
2 eggs
1/3 cup parmesan
salt
pepper

Extra parmesan for topping

Preheat oven to 400

Lay eggplant and zucchini out on a sheet pan, drizzle with oil, salt and pepper. Cook for 10 minutes, flip and cook for 10 more minutes.
Lay evenly in a baking pan.

Top with tomato sauce

Lay potatoes on sheet pan, drizzle with olive oil, salt and pepper. Cook for 10 minutes, flip over and cook ten more minutes, Lay on the Eggplant and zucchini. Reduce oven to 350.

Sprinkle with gruyere.

Mix together white sauce ingredients, spread on top of gruyere. Top with a little extra parm.

Bake in 350 oven for 30 minutes or until nicely browned,