Preheat the oven to 425 F. Place the squash on sheet pan with sides and drizzle with the oil, rosemary, salt and pepper. Mix well and roast until squash is browned and soft, about 25-30 minutes, turning after 15 minutes.

In a large bowl, combine warm squash with pesto; add grapes and cheese and gently toss. Divide the arugula among four serving plates, top with the squash mixture and serve.