Preheat an oven to 300°F. Add the garlic, cut-side down to a sauté pan and add the oil. Roast at 300°F for 20 to 30 minutes and then let cool. Remove the roasted garlic cloves from their skins and transfer the garlic and oil to the bowl of a food processor. Add the black pepper and fresh thyme and pulse until combined. Submerge steaks in marinade, cover, and refrigerate for a couple hours, or overnight before cooking.