Preheat oven to 400°F and line a baking sheet with parchment paper.
Chop sweet potatoes into 1/2-inch chunks. Try to make them around the same size so that they are all done cooking at the same time. Place sweet potatoes, oil, salt and pepper in a large bowl and toss to combine. Pour sweet potatoes onto parchment lined baking sheet (save some room for the chickpeas).
Add the chickpeas to a mixing bowl with oil and seasonings. Use your hands to coat the chickpeas well. Pour chickpeas onto a baking sheet, separate from the sweet potatoes.
Bake for 30-35 minutes, tossing once half-way through, until sweet potatoes are soft. Remove from oven, taste and season with additional salt if needed.
While sweet potatoes and chickpeas are roasting, rinse and drain quinoa, if needed. Add quinoa and broth to a saucepan and bring to a boil. Reduce to a simmer, cover and cook for 15 minutes. Fluff with a fork and let cool for 5-10 minutes.
Meanwhile make the dressing and set aside.
To make the bowls, add ½ cup quinoa, 1 cup spinach, ½ cup sweet potatoes, ⅓ cup chickpeas, ¼ cup cucumber, ¼ cup cabbage and 1 Tablespoon sunflower seeds to 4 bowls. Drizzle 2 Tablespoons of dressing and top with sliced avocado, if desired.