Preheat and prep: Heat the oven to 425°F (220°C). Line a large sheet pan with parchment for easier cleanup.
Season the sweet potatoes: Toss the cubes with 1 tbsp olive oil, half the spice blend, and a pinch of salt.
Spread on half the sheet pan.
Add the veggies: On the other half, toss onion, bell pepper, and broccoli with 1 tbsp olive oil, a pinch of salt, and black pepper. Roast for 12 minutes.
Season the chicken: Pat dry. Drizzle with 1 tbsp olive oil, then coat with the remaining spices.
Push the veggies to make space and add the chicken to the pan.
Roast to finish: Continue roasting 12–16 minutes, until the chicken reaches an internal temperature of 165°F (74°C) and the sweet potatoes are tender with caramelized edges. Rest chicken for 5 minutes, then slice.
Make the dressing: Whisk tahini, lemon juice, maple syrup, garlic, and salt. Add warm water, 1 tbsp at a time, until creamy and pourable.
Prep the base: Add a handful of greens to each bowl.
If using, spoon in 1/2 cup warm quinoa, rice, or farro.
Build the bowls: Divide sweet potatoes, roasted veggies, and sliced chicken. Top with avocado, seeds, and herbs.
Finish with sauce: Drizzle with lemon-tahini dressing. Serve with citrus wedges for extra brightness.