Preheat the oven to 400°F. Place the cauliflower on a baking sheet, drizzle with oil, and sprinkle with salt and pepper. Roast for 15-20 minutes.

While the cauliflower is roasting, trim the ends of the Brussels sprouts and "shred" the sprouts by cutting into small strips. Place into a large bowl. When the cauliflower is done roasting, place into the bowl with the Brussels sprouts.

Turn the oven to broil. Place the grapefruit slices on the same baking sheet and broil for about 3-5 minutes, watching closely to make sure they don’t burn. Remove from oven and set aside.

Heat a small skillet to medium, add the chopped hazelnuts and toast until they become fragrant (about 5 minutes) tossing often to prevent burning. Add to the bowl with Brussels sprouts and cauliflower.

Blend all dressing ingredients together in a blender until well combined.

Add breadcrumbs, Parmesan, and dressing to the salad bowl and toss.

Trim the grapefruit rind from the flesh and either cut the flesh into smaller pieces and toss into the salad or serve individual pieces on each salad plate. Garnish with more Parmesan, salt, and pepper, if desired.