Wrap the head of garlic with aluminum foil and roast for 40 minutes. Remove from the oven and let cool enough to handle.
Squeeze the garlic from its papery skins into a small glass bowl and combine together with the butter and ancho powder, mixing well. Season with salt and pepper. Place a piece of plastic wrap on a work surface, spoon the butter into the middle and roll into a cylinder. Refrigerate until firm, about 1 hour.
Prepare a barbecue to medium-high heat. Brush the steaks with olive oil and sprinkle with salt and freshly ground black pepper. Grill the steaks to desired doneness, about 6 minutes per side for medium doneness. Transfer to a platter and tent with foil to keep warm. To serve the steaks, top each with a pat of roasted garlic butter.
The compound butter can be made ahead and will keep in the refrigerator for up to a week.