Roasted Beets with Fennel, Mandarin Oranges and Pistachio Vinaigrette

Ingredients

• 12 tennis-ball-sized beets (red, gold, pink and/or white)
• 2 navel oranges
• 2 mandarin oranges, peel and pith removed and sliced crosswise
• 1 bulb fennel
• 1/4 cup cider vinegar
• 1/8 cup brown sugar
• Salt and freshly ground pepper, to taste
• 1/2 cup olive oil
• 1 cup roasted pistachios, coarsely ground in food processor
• 1 large handful of greens (mache, arugula, etc.)