Preheat oven to 180 degrees C. Coat a baking tray with the olive oil. Place the pumpkin and onion in the pan and season with salt and pepper. Roast 30 minutes, or until squash is tender.
Bring a large pot of lightly salted water to a boil. Place penne in the pot, cook for 8 to 10 minutes, until al dente, and drain.
In a large frypan over medium heat, cook the turkey mince until evenly brown. Transfer the cooked pumpkin and onion and the cooked pasta to the frypan. Gradually pour in the cream. Season with sage. Continue cooking until heated through. Mix in garlic. Transfer to a large bowl and toss with balsamic vinegar before serving.