Dry lamb thoroughly, then score the fat by making shallow cuts all over with tip of a sharp knife.
Using a mortar and pestle, pound garlic and sea salt into a paste, then combine with rosemary and pepper. If the paste seems a bit dry, add a little olive oil to loosen it up.
In a roasting pan, coat lamb with the seasoned paste all over, making sure that it is completely covered. Let stand for 30 minutes.
Preheat oven to 350 degrees.
Roast lamb in the oven until an instant read thermometer placed into the thickest part of the meat registers 125° to 130°F for medium-rare, or 130° to 135°F for medium. This should take ~1.5 hours.
Remove the meat from the pan, and let meat rest for 20 minutes before carving.
Optional sauce: Add wine to roasting pan and deglaze by boiling over moderately high heat, stirring and scraping up all the brown bits. This should take approximately 1 minute. Season pan juices with salt and pepper and serve with lamb.