Place an oven rack in the center position and preheat the oven to 400 degrees F.
While leaving the bulb intact so the cloves stay connected, peel away most of the papery outer layers of the garlic.
Using a sharp knife, slice off about 1/4-inch from the top of the garlic, exposing the tips of the cloves. (Note: you want to slice the pointy stem end, not the root end with the little hairs. That's the side holding the cloves together).
Place the clove in a small ramekin, sliced side up. Drizzle 1-2 teaspoons of olive oil over the exposed cloves, then sprinkle lightly with salt. Top the ramekin with aluminum foil. (Note: if you don't have a ramekin, you can lay the garlic down on a piece of foil, then wrap it up after adding the oil and salt).
Place the ramekin in the oven and roast for 35-40 minutes. The exact time will depend on the size of the bulb. You'll know it's ready when the cloves are completely soft and caramelized. If you like, you can continue pushing that caramelization for another 10-15 minutes to deepen the flavor.
Let the garlic rest until it's cool enough to handle, then squeeze the bulb to remove the cloves.
Use immediately, refrigerate for up to 1 week, or freeze for up to 3 months.
This recipe can be scaled up to roast as much garlic as you need. If you're roasting several heads at once, you can skip the ramekin and securely wrap each one individually in foil. Place them on a baking sheet to avoid any oil drips in the oven.