Preheat the oven to 425 degrees F (220 C). Arrange the fresh, seasonal veggies on a rimmed baking pan. Toss with a little bit of olive oil and salt.
Peel the 3 garlic cloves. Place them in the center of a small piece of foil, drizzle with a little oil, and wrap it up. Place on the baking pan with the veggies. Roast everything for 20-30 minutes (depends on what kind of veggies you’re using). When done, mash the roasted garlic so it makes a paste.
While the veggies roast, pulse the walnuts, basil leaves, 1/4 cup olive oil, the very small clove of garlic, and lemon juice in a food processor until a smooth pesto forms.
Also while the veggies roast, cook pasta according to package directions until al dente. Drain, reserving some pasta water, then toss with a little oil, and set aside.
Combine the roasted vegetables, mashed roasted garlic, cooked pasta, and the walnut pesto in a large bowl. Toss to combine, adding a splash of reserved pasta water if needed to reach desired consistency. Serve immediately, seasoned with extra salt to taste.