Heat oven to 350 F.
Spray large rimmed baking sheet with nonstick spray.
Combine butternut squash, carrots, rutabagas, summer squash and sweet potatoes in a large bowl.
Add oil and cayenne; toss to coat. Sprinkle with salt and pepper.
Spread vegetable mixture on prepared baking sheet. Roast until vegetables are tender, stirring and turning occasionally, about 1 hour.
Transfer vegetable mixture to bowl. Add red onion, chives and vinegar; toss to blend. Season with additional salt and pepper to taste.