Preheat oven to 450 degrees.
Dry all lamb shanks with paper towel and then mix onion powder, greek seasoning, cumin, salt, and pepper into a bowl. Drizzle a little olive oil to lightly coat the top of shanks and then rub on the dry seasoning.
Lay garlic on a roasting pan and then lay the seasoned shanks on top. Roast at 450 degrees for 25 minutes or until browned. Prepare remaining wet/dry ingredients while shanks are cooking by mixing the lemon, wine, parsley, oregano, and olive oil together.
Remove shanks from the oven and reduce the temperature to 350 degrees. Pour wet ingredients into pan along with two of the leftover lemon rinds. Cover with foil and cook for 1 hour. While shanks are cooking, prepare potatoes by peeling them and cutting them into wedges.
Remove foil and add ¼-1/2 cup water. Arrange wedged potatoes around the outer edges of the pan. Use a spoon to drizzle pan juices over the top and generously season potatoes with salt and pepper. Cover roasting pan again with foil and cook for an addition 1 to 1 ½ hours, or until potatoes are tender and meat pulls easily from the bone.
Remove pan. Plate shanks and potatoes then drizzle with leftover juices. Garnish with more parsley if desired.