Cut 1 small cauliflower into large florets. Toss with 2 tablespoons olive oil on a foil-lined baking sheet; season with salt and pepper. Roast at 450˚ F, tossing halfway through, until browned and tender, 25 to 30 minutes. Mix 1 tablespoon each Dijon mustard and date syrup and 1 teaspoon balsamic vinegar. Pour over the cauliflower and toss; roast until glazed, 10 minutes. Sprinkle with parsley.