Preheat the oven to 450 degrees F (230 degrees C).

Heat 1 tablespoon oil in a skillet over medium heat. Add sausage links and cook until browned and fat begins to render, about 3 minutes per side. While they cook, lightly pierce sausages in several places with the tip of a sharp knife to release fats and juices. Remove from the heat and place on a cutting board to cool slightly, 3 to 5 minutes.

Cut cooled sausages into 2-inch slices; return to the skillet along with any accumulated juices from the cutting board.

Cut two slashes down to the bone on the skin side of each chicken thigh. Halve or quarter any large peppers.

Place chicken and peppers into a large mixing bowl with onions, sausage and juices, Italian herbs, salt, and pepper. Drizzle with remaining 1 tablespoon oil and mix with your hands until all ingredients are coated in oil, 3 to 4 minutes.

Transfer mixture to a large, heavy-duty roasting pan. Evenly space chicken thighs with the skin facing up and position potatoes near the top.

Roast in the preheated oven until chicken is cooked through and everything is caramelized, about 1 hour. An instant-read thermometer inserted near the bone should read 165 degrees F (74 degrees C). Sprinkle with chopped fresh Italian parsley.