For the salad: Preheat oven to 425F. Combine the beets, squash, and shallots in a roasting pan and drizzle them with olive oil. Sprinkle a generous pinch of salt and roast, stirring now and then, until cooked through and nicely caramelized, about 35 minutes.
For the vinaigrette: Whisk together the mustard, vinegar, and maple syrup in a mixing bowl. Add the oil slowly then season with salt and pepper.