Preheat the oven to 400°F.

Cut the top off the head of garlic, exposing the cloves. Rub cloves with olive oil. Wrap in a square of foil and roast in the oven for 30 minutes. Let cool, then scoop out roasted cloves and set aside.

Cut avocados in half and scoop flesh into a bowl, discarding pits. Mash slightly. Add roasted cloves, green onions, cilantro, and salt, and mix well, mashing garlic cloves if desired. Stir in lime juice to taste, then serve.