Prepare the sweet potatoes: Toss the diced sweet potatoes with olive oil, salt, and pepper. Spread on a baking sheet and roast for 25-30 minutes, flipping halfway, until tender and slightly caramelized.
Season the chicken: In a small bowl, mix smoked paprika, garlic powder, onion powder, cayenne, oregano, thyme, salt, and pepper. Rub the chicken breasts with olive oil and coat evenly with the spice mixture.
Cook the chicken: Heat a skillet over medium-high heat. Sear the chicken for 4-5 minutes on each side until blackened and cooked through. Let rest for a few minutes, then slice.
Prepare the avocado dressing: In a blender, combine avocado, Greek yogurt, lime juice, garlic, olive oil, and salt. Blend until smooth, adding water as needed for a pourable consistency.
Assemble the bowls: Divide cooked brown rice or quinoa among serving bowls. Top with roasted sweet potatoes, sliced chicken, arugula, cherry tomatoes, cucumber, and avocado slices. Drizzle with avocado dressing and serve immediately.