In a large Dutch oven, mix all of the ingredients except the chicken; stir to blend, and add the chicken. Turn to coat. Cover and cook for 45 minutes over medium-low heat, until the chicken is tender.
In a medium saucepan, about 15 minutes before serving, combine the broth, turmeric, and roasted red pepper. Cover and bring to a boil. Remove the pan from the heat, stir in the couscous, and let stand for 5 minutes. To serve, spoon the couscous onto a serving platter, arrange the chicken on top, and pour the sauce from the Dutch oven over the chicken. Sprinkle with sesame seeds, if desired.