Preheat oven to 425°F.
In a medium saucepan heat 2 Tbsp. olive oil over medium heat. Add chopped red onion and sauté 3-5 minutes, until tender.
Add minced garlic and sauté for 1 minute or until fragrant.
Add uncooked Arborio rice; sauté, stirring constantly, 2 minutes.
Stir in chicken broth and a dash of pepper. Bring to a boil; reduce heat. Cover and simmer 20 minutes.
While rice is simmering, spread 8 cups chopped fresh vegetables on a large rimmed baking sheet. Drizzle with 1/8 cup olive oil, 1/4 cup balsamic vinegar, and 1 teaspoon kosher salt.
Roast at 425° for 25 minutes, stirring halfway through.
When rice is finished, let stand, covered, 5 minutes. Stir in Parmesan cheese.
Serve balsamic vegetables over risotto; season with additional kosher salt or balsamic vinegar as desired.