Position a rack in the center of the oven and preheat the oven to 400°F.
Slice about 1⁄2 inch from the top of each head of garlic. Arrange the garlic cut side up on a large sheet of heavy-duty aluminum foil. Drizzle with 2 Tbs. of the oil and season with 1⁄4 tsp. each salt and pepper. Add a few thyme sprigs and wrap the foil tightly to make a packet.
Roast until the cloves are light golden-brown and very soft, 45 minutes to h hour. Remove from the oven and let cool.
To remove the garlic from the heads, squeeze the cloves from the bottom intoa small bowl and mash with a fork.
Notes
You can store the roasted garlic in an airtight container in the refrigerator for up to 2 weeks, or freeze for up to 1 month.