To make the main spice blend: Mix together the fennel seeds, sumac, pimentón, Aleppo pepper, and cinnamon.
To roast the vegetables: Position racks in the upper and lower thirds of the oven and preheat the oven to 375°F. Line two half sheet pans with foil.
Combine the spice blend, vinegar, oil, and 1 teaspoon salt in a very large bowl and stir to mix well. Add the Brussels sprouts, radishes, garlic, beets, turnips, carrots, shallots, sweet potatoes, and celery root and toss well until evenly coated.
Divide the vegetables between the prepared pans and spread them evenly. Roast, stirring the vegetables and switching the positions of the pans halfway through, until tender, 45 to 60 minutes. Drizzle with more oil, season to taste with salt, and serve hot, warm, or at room temperature.
To make ahead: The roasted vegetables can be refrigerated for up to 1 week.