Heat the oven to 425°F. Place the cauliflower on a rimmed baking sheet. Mix the oil, coriander, cumin, paprika, garlic and 2 teaspoons each salt and pepper.
Brush the mixture onto the cauliflower, then roast until deeply browned and a skewer inserted into the center meets no resistance, 55 to 70 minutes. Cut into wedges and sprinkle with mint.
