Preheat your oven to 400°F (205°C) and line a large rimmed baking sheet with parchment paper.
In a small bowl, prepare the rub by whisking together the minced garlic, smoked paprika, cumin, chili powder, caraway, lemon zest, ½ tsp kosher salt, and black pepper. Pour in ¼ cup of the extra virgin olive oil (reserving the rest) and stir until a fragrant paste forms.
Place the diced sweet potatoes, rinsed chickpeas, and red onion wedges directly onto the prepared baking sheet. Drizzle with the remaining olive oil. Add half of the prepared harissa rub to the pan and use your hands to toss everything together until evenly coated. Spread the mixture into a single, even layer.
Pat the chicken breast chunks dry and place them in a large bowl. Add the remaining harissa rub and toss until the chicken is thoroughly coated on all sides. Arrange the coated chicken pieces amongst the vegetables on the sheet pan, ensuring nothing is overcrowded. Use a second sheet pan if necessary.
Transfer the sheet pan to the oven and roast for 25-30 minutes. The chicken is done when its internal temperature reaches 165°F (74°C) and the sweet potatoes are tender.
While the chicken and vegetables roast, prepare the sauce. Combine all sauce ingredients—Greek yogurt, cilantro, parsley, mint, lemon juice, 1 tbsp olive oil, and ¼ tsp salt—in a blender. Blend until completely smooth and vibrantly green.
To serve, divide the roasted vegetable and chickpea medley among six bowls. Top each with a portion of the harissa-rubbed chicken. Drizzle generously with the trio-herb yogurt sauce.