For the roast chicken: Preheat the oven to 400 degrees F.
Place the chicken on a dishwasher-safe cutting board. Combine the coconut milk, red curry paste and palm sugar in a medium bowl and stir until the sugar is dissolved.
Slather the curry rub all over the chicken. (You can marinate the chicken in the refrigerator for up to 8 hours if desired.) Stuff the chicken cavity with the lemongrass, shallot, lime peel, lemon wedge and half of the scallions.
Roast the chicken in a roasting pan for 30 minutes, lower the oven temperature to 325 degrees F and continue roasting until the internal temperature of the chicken reaches 165 degrees F, about 1 hour more.
When the chicken is cool enough to handle, shred into bite-sized pieces and set aside.
For the red curry citrus dressing: Whisk together the lemon juice, lime juice, red curry paste, fish sauce and sugar in a small bowl until the sugar is dissolved. Whisk in the vegetable oil.
To serve: Bring 4 to 6 quarts water to a boil in a medium saucepan. Add 1/4 teaspoon salt and the egg noodles and boil until al dente, 6 minutes. (For more tender noodles, boil for 1 minute more.) Drain well.
Place the egg noodles on a serving platter. Top with the bell pepper, bean sprouts, basil and mint. Add a generous handful of the shredded chicken and garnish with the chile, lime leaf and remaining scallions. Serve with the red curry citrus dressing on the side and garnish with the lime wedges.