Preheat the oven to 400 degrees F and soak the Cocorico Roaster in cold water for 30 minutes.
In a 2 quart saucepan, place the potatoes and enough water to cover them by 2 inches. Add 1 tablespoon of Gray salt and bring the water to a boil. Cook the potatoes for three or four minutes. Strain liquid and reserve the potatoes.
Rinse the chicken inside-out and dry well. Coat inside and outside with half the olive oil. Season the chicken on the outside with 2 tablespoons of the seasoning salt. Place the rosemary sprigs and lemon inside the cavity of the chicken. Carefully place the chicken onto the Cocorico Roaster, legs facing up. Put the Cocorico in the center of the oven. Roast the chicken for 15 minutes.
During this time, core the bell peppers and cut them into 1-inch wide lengths. Halve the onions. In a bowl toss the potatoes, bell peppers and onions with the remaining olive oil and seasoning salt. Place in the tray of the Cocorico.
Reduce the heat to 375 degrees F and continue roasting, about 1 hour, until the juices run clear when the thigh is pierced with a skewer. Every 15 minutes, rotate the Cocorico by at least 1/4-turn. Remove from the oven and let rest for 15 minutes. Carefully remove the chicken from the Cocorico and carve into serving portions. Transfer to a platter and serve with the roasted vegetables.