Heat your oven to 425°F (really hot!). Put one oven rack on the lowest level and another in the middle.
In a big bowl, mix the potato wedges with olive oil, salt, pepper, and oregano until they're all covered.
Spread the potatoes out on a baking sheet. If you have lots of potatoes, you might need two baking sheets.
Put the baking sheet(s) in the oven on the bottom rack and let the potatoes cook for about 15 minutes. Then, take them out and flip them over.
After flipping the potatoes, add the sliced onions on top, and then lay the sausages over everything.
Put the baking sheet(s) back in the oven on the middle rack and cook for another 30 minutes or until the sausages are cooked through.
If you want the sausages to look extra golden, switch the oven to broil for the last 1-3 minutes. But keep an eye on them!
When everything's done, sprinkle the minced parsley over the top. Serve with cherry peppers and/or Pecorino Romano cheese on the side. Enjoy!