1. Preheat oven to 425 degrees Fahrenheit. Line a baking sheet with foil. Peel golden and red beets and place on baking sheet. Drizzle with two tablespoons olive oil. Roast for 40 to 45 minutes until golden brown and soft enough to slice. Set aside and cool.
2. In a small bowl, whisk balsamic vinegar, orange juice, honey, mustard, salt, and pepper. While whisking, slowly drizzle in remaining one-third cup olive oil until emulsified.
3. Peel oranges and grapefruit, removing peel and white pith; cut crosswise into one-eighth- to one-fourth-inch-thick slices. Slice beets into equal slices.
4. Arrange spinach, arugula, and radicchio leaves on a large round platter. Place orange and grapefruit slices, beets, and fennel slices atop mixed greens in a decorative pattern. Sprinkle with pomegranate seeds and pistachios. Drizzle with dressing.