Preheat oven to 375-degrees. To roast the head of garlic, cut the top ¼-inch off the top. Place garlic on a 6-inch x 6-inch piece of foil. Drizzle olive oil over the garlic; close the foil around the garlic and roast in oven for about an hour. The garlic will be soft and golden when done. When ready to use, you can easily squeeze the garlic cloves right out of the skin.
Place potatoes in a large pot or Dutch oven; cover with cold water. Add 1 teaspoon salt; bring to a boil. Simmer for 15 minutes, or until fork tender. Drain and return potatoes to pot; add the roasted garlic cloves.
Gently warm the half & half and butter until butter is melted (this can be done on the stovetop or microwave). Add to the pot with the potatoes and garlic, along with salt and pepper. Mash until milk and butter are incorporated and potatoes are a creamy consistency with some lumps. Garnish with fresh herbs and more butter, if desired