Roasted Root Vegetable Frittata

Name: Roasted Root Vegetable Frittata
Ingredients: 1/2 cup large diced parsnip; 3/4 cup large diced carrots; 1 1/4 cups large diced sweet potatoes; 1 1/2 cups leeks; 1 cup yellow onion; 8 large eggs; 1/3 cup whole milk; 2 pieces thick-cut bacon; 1 1/2 teaspoons minced fresh thyme leaves; 1/4 cup olive oil, divided; kosher salt; ground black pepper; non-stick spray