Preheat oven to 425 degrees Fahrenheit.
In a medium stock pot of boiling water, place two lemons and the potatoes and boil for 7 minutes. Drain the potatoes and allow them to dry. Slice the lemons in half. Stuff the chicken with the lemons and 1/2 cup of parsley. Set aside.
Place the potatoes in a small roasting pan (11 x 14-inches), toss with a little olive oil and season liberally with salt and pepper. Add all but 3 cloves of garlic evenly throughout the potatoes.
Pat the outside of the chicken dry, coat with olive oil, and liberally season with salt and pepper. Place chicken on top of the potatoes. Slice the Kielbasa sausages at an angle about 1/2 inch thick. Sprinkle the sliced sausage and 1/4 cup of the parsley over the top of the chicken and potatoes. Roast in the preheated oven for 1 hour and 20 minutes.
While the chicken is cooking, make the gremolata. Zest the remaining two lemons and chop th zest, remaining parsley, remaining 3 cloves of garlic, and a pinch of salt and pepper.
When the internal temperature of the chicken reaches 160 degrees, remove the chicken from the oven and set aside. Shake the potatoes around and place back into the oven for about 5 to 8 minutes, or until the potatoes are slightly golden and crunchy on the outside. Remove the potatoes from the oven.
Divide the carved chicken and potatoes among 8 to 10 plates. Sprinkle the gremolata over the top of the chicken and potatoes on each dish. Serve with salad and crusty bread.