Sweet Potatoes - Poke holes on all sides of each sweet potato. Rub the potatoes with olive oil and sprinkle with sea salt. Roast for 1 hour, or until easily pierced with a fork.
Remove the sweet potatoes from the oven, let them cool for 10 minutes or until you can safely handle them. Cut each potato in half and scoop out the insides into a large bowl but leave a thin layer to support the skin. Be very careful to not tear the skin.
Filling - (While the potatoes are roasting) Sauté the onions in 2 tbsp of olive oil for 5-8 minutes. Add the balsamic vinegar, stir to combine and cook for 1-2 additional minutes until all the vinegar has been absorbed.
Add the balsamic onions, garlic powder, dried rosemary, salt, pepper, and half of the goat cheese to the sweet potato filling. Mix until the cheese is fully combined. Scoop the mixture back into the potato skins, top with extra goat cheese, parmesan cheese, and a sprinkle of rosemary. Put the tray back in the oven for 15 minutes.
Remove the sweet potatoes from the oven, drizzle balsamic glaze over the top and a sprinkle of parsley to garnish.