Preheat oven to 425°F.
Place carrots and fennel on a rimmed baking sheet and drizzle with oil. Season with salt, turmeric, cumin, and chili powder and toss. Spread evenly so that there is little to no overlap. Roast vegetables for 25 to 30 minutes, until vegetables are tender and browned.
While the vegetables are roasting, make the lemon-tahini sauce. Stir tahini, lemon juice, and 1 tablespoon warm water together in a small bowl. If it needs to be looser, add the second tablespoon of warm water.
Divide the quinoa, spinach, veggies, orange segments, avocado, and cashews between 4 bowls. Drizzle with lemon-tahini sauce and serve immediately.