Preheat an oven to 400°F.
In a small bowl, stir together 2 Tbs. extra-virgin olive oil, 1/2 tsp. kosher salt, 1 tsp. curry powder and 1/4 tsp. cayenne pepper.
Drizzle over the cauliflower, toss to coat evenly.
Arrange the cauliflower florets in a single layer on a rimmed baking sheet.
Roast the cauliflower, stirring 1 or 2 times, until golden brown and crisp-tender, 25 to 35 minutes.
When the cauliflower is done, in a small bowl, stir together 1/2 cup plain yogurt and 1 Tbs. Dijon mustard.
Pour over the hot cauliflower and serve immediately