Preheat oven to 400 degrees. Line a rimmed baking sheet with unbleached parchment paper.
Brush the cut side of each cabbage round with oil and place in one layer on the prepared sheet. Sprinkle with salt and pepper to taste.
Roast cabbage, about 40-45 minutes, flipping over after 20 minutes. Cabbage should be tender and lightly golden around the edges.
Whisk dressing ingredients together in a medium bowl. Drizzle cabbage with dressing if desired.