Preheat the oven to 375°F. With a large, sharp knife, cut off the top of a whole head of garlic to expose the very top of the cloves. Drizzle with a little olive oil and season with salt and pepper. Wrap each head loosely in foil and roast for 45 minutes or until the head is soft when gently squeezed. Open the foil and roast for another 5 to 10 minutes to lightly brown and caramelize the garlic. Remove from the oven, let cool, and squeeze the garlic out of the husks—like squeezing toothpaste out of a tube. Store tightly covered in the refrigerator for up to 10 days.