Rinse the lamb steaks and set aside.
Grate the outer zest from half of the lemon into a large ziplock bag. Squeeze all of the lemon juice into the bag. Add oil, rosemary, garlic, salt, pepper, and paprika. Stir. Shake to mix, then pour 1/4 cup of mixture into a small bowl and set aside.
Add the lamb to the bag, massaging it to coat it with the marinade. Press out the air and seal the bag. Refrigerate for at least 2 hours or up to 8 hours.
Heat a grill for medium-high heat. Scrape grill rack clean and coat with oil. Pull the steaks from marinade, and grill them directly over the heat until marked by the grill and medium-rare in center (about 135ºF internal temperature), 3 to 4 minutes per side. Avoid cooking beyond medium-rare, or the lamb will be tough. Transfer to plates and let sit for 5 minutes.
Brush one side of the bread slices with a small amount of reserved marinade and grill, oiled-side down, just until marked by the grill, 1 to 2 minutes.
Just before serving, drizzle the steaks with the remaining marinade and scatter on the mint. Serve with the grilled bread.
Tip: If you can’t find lamb leg steaks in the meat case, ask your butcher to cut them. You want bone-in leg steaks, about 1/2-inch thick or less.