Heat the oven to 475ºF with an oven rack in the middle position. Line a rimmed baking sheet with foil. In a large bowl, combine the oil, curry powder, cumin, salt and pepper. Add the cauliflower and toss. Transfer to the prepared baking sheet, reserving the bowl.

Arrange the pieces cut side down. Roast until well browned, about 30 minutes. Let cool. In the reserved bowl, combine the mint with the dressing. Add the cauliflower and toss to coat.