Heat oven to 350 degrees.
Remove the outer leaves from the cauliflower head and trim the center core so that it is flush with the base of the cauliflower head. You are trying to get the cauliflower to sit up straight on the flat surface of a skillet or roasting pan.
Rub the cauliflower head all over with 2 tablespoons olive oil. Sprinkle with salt. Place the cauliflower in a 10- to 12-inch cast iron skillet, add about ¼ cup of hot water to the skillet, wrap the cauliflower with aluminum foil and seal around the pan as best you can.
Drizzle garlic cloves with 1 tablespoon olive oil. Wrap cloves in a square of aluminum foil.
Place pan and foil packet with garlic cloves in oven and roast cauliflower for 45 minutes, or until a fork inserted into a floret goes in and out easily.
Remove garlic cloves from oven, cool, then peel. Remove foil from cauliflower, and roast uncovered for 15 minutes or until florets start to brown and "dry out" a little.
Remove cauliflower from oven and allow to cool slightly.