Preparation

Roast the vegetables

• Position racks in the upper and lower thirds of the oven and heat the oven to 450°F.
• In a large bowl, toss the beets with 1 Tbs. of the oil and 1/2 tsp. salt. Transfer to a large rimmed heavy-duty baking sheet. Spread into a single layer.
• In another large bowl, combine the turnips and potatoes with the remaining 1 Tbs. of oil and another 1/2 tsp salt. Transfer to a large rimmed heavy-duty baking sheet. Spread into a single layer.
• Roast the vegetables, flipping with a spatula halfway through and rotating the baking sheets, until browned and tender, 20 to 25 minutes. Let cool for a few minutes on the sheets. Transfer to a large bowl.

Make the vinaigrette

• Heat the oil in a 8-inch skillet over medium heat. Add the onion and a pinch of salt and cook, stirring occasionally, until softened and lightly browned, 2 to 4 minutes. Add the garlic and cook, stirring, until fragrant and softened, about 15 seconds. Remove from the heat. Let the oil cool for 3 to 5 minutes.
• Meanwhile, in a small heatproof bowl, whisk the vinegar, honey, orange juice, zest, thyme, mustard, 1/4 tsp. salt, and several grinds of fresh pepper. Whisk the warm oil into the vinegar mixture until emulsified.
• Season to taste, adding more orange juice, salt, or pepper as needed.

Assemble the salad

• In a large bowl, combine the frisee, radicchio, and parsley leaves. Lightly season  with salt and then drizzle with 2 Tbs. of the warm vinaigrette. Toss, taste, and add a little more dressing, if necessary. Arrange the greens on a platter or plates.
• Season the roasted vegetables with a pinch more salt, and dress them lightly with 1 to 2 Tbs. of the remaining vinaigrette. Scatter over the greens, then top with the hazelnuts. Serve right away, passing the remaining dressing at the table.