Adapted liberally from Ina Garten.
Preheat the oven to 400 degrees. Place the butternut squash on a sheet pan. Add 2 tablespoons olive oil, 1 teaspoon salt and 1/2 teaspoon pepper and toss. Roast the squash for 20-25 minutes, turning once, until tender. Meanwhile, make your dressing by whisking all ingredients together in a bowl, and adding salt and pepper to taste.
Place the arugula in a large salad bowl and add the roasted squash mixture, the walnuts, and cranberries. Spoon just enough vinaigrette over the salad to moisten and toss well. Serve immediately. [The salad can also be made a day in advance. Toss with dressing immediately before serving.]