Thaw the filo at room temperature.
Make the chickpea-seitan filling:
Heat the extra virgin olive oil. Add the onions and garlic and a pinch of salt and ground black pepper. Saute until the onions are soft and look cooked.
Add the mushrooms, stir to mix, then add the diced tomatoes, paprika, and herbs.
Let the mixture cook, stirring frequently, until it darkens and most of the liquid from the tomatoes has evaporated.
In a food processor, pulse the chickpeas and seitan until they are crumbly but not pasty. You want some texture.
Add this to the tomato and herb mixture and stir well to mix. Let the filling cook about 10 minutes more on medium heat, so all the flavor mix well. Check seasoning and add more salt and black pepper if needed. Turn off the heat and set aside.
Make the roasted veggies:
Toss the red peppers and onions with salt and ground black pepper and olive oil. Spread in a single layer on a baking sheet and bake in a preheated 350-degree oven for 30 minutes or until the onions are slightly browned at the edges. Set aside.
Assemble the lasagna:
Brush the bottom of a 9 X 12 inch baking dish with some olive oil. Place a single filo sheet on top. Work carefully but don't fret if it tears-- filo is very forgiving and by the time you are done adding on all those layers no one will know.
Brush or spray the filo sheet with some olive oil and place another sheet on top of it. Brush or spray with oil again. Repeat this until you have layered seven sheets.
Spread the seitan-chickpea filling in an even layer on the filo.
Continue layering the filo sheets on top, spraying each sheet with oil, until you have added six more sheets. Now spread the roasted veggies on top in a single layer.
Layer on the remaining seven sheets, spraying with oil after each layer is added. Spray some oil on the top sheet.
Preheat the oven to 375 degrees.
Cover the baking dish with some aluminum foil and bake 20 minutes.
Remove the foil and continue baking another 3 minutes or until the top is lightly golden-brown.
Let stand a few minutes before cutting.