Toss the squash with the two tablespoons of olive oil and salt and pepper to taste.
Place on a foil-covered roasting pan and roast at 425°F until the squash is cooked and has caramelized on the outside, tossing gently every few minutes. This should take about 20 minutes or so. Set aside and keep warm.
Heat the one tablespoon of oil and the butter in a heavy-bottomed saucepan. Add the couscous and cook for three or four minutes, stirring frequently, until at least some of the couscous takes on a golden brown color.
Add the onion and a bit more salt and pepper, and cook until the onion has softened. You may need to add a bit more oil and/or butter. If you do not want to add more fat, add just a bit of water to keep the couscous and onion from sticking.
Bring the stock and orange juice to a boil in a pan or microwave.
Add the stock mixture all at once. Add the poultry seasoning. Bring everything to a boil, then cover and reduce the heat to a simmer.
Cook until the couscous has absorbed almost all of the stock. Stir in the cranberries, the reserved squash, and the rosemary.
Taste for seasoning and adjust as necessary.