Take your heads of garlic and cut the top "pointed" ends off to expose the garlic cloves. You do want to cut far enough down that you have cut the top of the cloves off.
*optional* I personally drizzle olive oil over mine but you dont have to.
Wrap loosely in aluminum foil and pop it in the oven for 40-45 minutes. If you're doing more than one for a fridge stock (making a ton to put in the fridge to have on hand) then you can just set them cut side up in a pan and cover the whole pan in foil.
After 45 minutes pull out of the oven and let cool enough to handle and just squeeze the roasted cloves out of the wrapping.
It's as simple as that and now you have wonderfully roasted garlic for sauces, breads or just about any other application that you can use it for.