Position racks in the upper and lower thirds your oven and preheat the oven to 400 degrees F. Lightly coat 2 large baking sheets with nonstick spray. Lightly mist a 9x13-inch casserole dish with nonstick spray and set aside.

Place the vegetables in a large bowl and drizzle with the olive oil. Sprinkle with salt and pepper, then toss to coat. Divide the vegetables evenly between the two sheets and spread them into a single layer. Roast the vegetables until tender, about 20 minutes, tossing the vegetables on the pan so they cook evenly and switching the pans’ positions on the upper and lower racks once halfway through. Transfer half of the roasted vegetables to the prepared casserole dish and spread into an even layer. Reduce the oven temperature to 350 degrees F.

Meanwhile, in a large mixing bowl, beat the eggs together with the milk, garlic, and Italian seasoning until evenly blended. Gently pour it into the casserole dish. Scatter the remaining vegetables evenly over the top, then dollop the ricotta over the top in small spoonfuls (I like to add about 20 to 24 spoonfuls; you want to each slice to have a few dollops, but have them be large enough so that you can actually taste them).