1 lb beets, peeled, cut into ½” wedges
4 tablespoons olive oil, divided
Kosher salt, freshly ground black pepper
1 lb carrots, sliced 1/4” thick
1 lb Jerusalem artichokes (also called sunchokes), unpeeled, sliced ¼” thick
1 teaspoon finely grated lemon zest
1/4 teaspoon Aleppo pepper or hot paprika, plus more to taste
2 teaspoons fresh lemon juice, divided, plus more to taste
2 cups watercress, large stems trimmed
1/4 cup green tahini sauce (see related)
Optional: To save time, instead of green tahini sauce, thin some tahini with a combination of water and lemon juice. Grate ½ garlic clove, stir in, and season with salt.
Preheat oven to 425°. Toss beets with 1 Tbsp. oil on a lightly oiled rimmed baking sheet; arrange in a single layer and season with salt and black pepper. Roast 20 minutes, then turn over wedges and continue to roast until beets are tender and darkened around the edges, about 30 minutes total.
Toss carrots with 1 Tbsp. oil on one half of a lightly oiled rimmed baking sheet. Toss Jerusalem artichokes with 1 Tbsp. oil on the other half of the baking sheet. Arrange carrots and Jerusalem artichokes in a single layer, season with salt and black pepper, and roast until vegetables are lightly browned, about 20 minutes.
Toss all the warm roasted vegetables together with lemon zest, 1/4 tsp. Aleppo pepper, and 1 tsp. lemon juice. Season with salt, Aleppo pepper, and lemon juice.
Toss watercress with remaining 1 Tbsp. olive oil and 1 tsp. lemon juice; season to taste with salt and black pepper. Serve roasted vegetables with dressed watercress and tahini sauce.