Preheat your oven to 400°F. Line a large rimmed baking sheet with parchment paper. Add the broccoli, cauliflower, shallots and toss with the olive oil, herb blend seasoning, salt and pepper to taste. Spread them out evenly then add in your garlic head and drizzle it with olive oil and season with salt and pepper. Roast this tray for 40-45 minutes.
Warm your chicken broth through and add it to your blender along with the roasted broccoli, cauliflower and shallots. Squeeze the garlic out and into the blender too. Process this until its nice and smooth. Taste the soup and adjust the salt and pepper if needed.
I topped mine with crumbled bacon and chili pepper flakes but that is optional.