Preheat oven to 400°; line rimmed baking pan with parchment paper. In large bowl, whisk oil, turmeric, cumin, paprika, salt and black pepper; stir in bell peppers and potatoes. Spread bell pepper mixture in single layer on prepared pan; roast 25 minutes or until potatoes are fork-tender and golden brown. Stir in garlic and spinach; roast 3 minutes or until spinach is wilted. Makes about 5 cups.
Serve sweet potato mixture garnished with cilantro, if desired.