Heat oven to 400°F Cut top of garlic bulb off so that the majority of the cloves are exposed. Place in a small oven proof dish, pour 2 tablespoons olive oil over garlic bulb, and roast at for 30 minutes or until garlic is soft.
Arrange sliced cauliflower on a rimmed baking sheet, brush with additional olive oil and sprinkle with 1/2-1 teaspoon of the lemon pepper. Place in the oven beside the garlic and roast for about 10 minutes, stirring midway through, until cauliflower is lightly browned. Remove cauliflower from oven and set aside. When garlic is soft and top is lightly browned, remove from oven, place garlic bulb on a plate and let cool. Reserve roasted garlic oil for garnish, if desired.
Cook bacon in a medium sauce pan until crisp and fat is rendered. Drain on paper towel, crumble, and set aside. While bacon is cooking, finely chop 1/2 cup of the roasted cauliflower and reserve.
Cook onion and parsnip in bacon fat in the same sauce pan over med heat until vegetables are softened, about 5-6 minutes. Add cauliflower except for the reserved 1/2 cup to the onions and parsnips. Squeeze the garlic bulb from the bottom to remove garlic cloves and add cloves to the pot.
Pour 1 1/2 cups of the broth over the vegetables and simmer for 8-10 minutes or until vegetables are all cooked through. Puree soup in a blender until smooth, return to sauce pan and add remaining broth, reserved cauliflower, and cream.
Heat on low for 2 minutes to heat through. Serve in warmed bowls and garnish with crumbled bacon, scallions, and drizzle with reserved roasted garlic olive oil.