Preheat oven to 400 degrees F. Tightly wrap beets, separated by color, in aluminum foil bundles. Place on middle oven rack. Roast 45 minutes to 1 hour, or until tender when tested with a sharp knife. Remove from the oven; cool slightly. Peel the beets and set aside.
Place squash slices on a rimmed baking sheet. Toss with salt, pepper and 1 Tbsp. olive oil. Place on middle rack in oven and roast 15 minutes. Drizzle 1/3 cup maple syrup over squash, and roast another 10 minutes, or until tender. Cool.
To make dressing, in a small bowl, whisk the mustard, lemon juice and 1/4 cup maple syrup. Add the 1/3 cup olive oil and whisk till smooth. Season to taste.
To assemble, place salad greens in the middle of a large plate. Arrange beets and squash on lettuce. Pour half of the dressing over the salad. Sprinkle with pomegranate seeds. Pass remaining dressing. Makes 6 to 8 servings.