1. Preheat oven to 450°.
2. Toss together first 8 ingredients in a large bowl until vegetables are evenly coated. Spread in a single layer in 1 (15- x 10- x 1-inch) jellyroll pan or 2 (13- x 9-inch) baking dishes.
3. Roast, stirring once halfway through cook time, at 450° for 30 minutes or until edges of vegetables are light brown and tender when pierced with the tip of a knife.
4. Remove pan from oven. Add spinach to pan; toss gently with vegetable mixture until spinach is slightly wilted. Garnish, if desired, and serve warm or at room temperature.
When roasting vegetables, take care not to crowd your pan or else the vegetables will steam instead of caramelizing and browning around the edges.