Preheat the oven to 200 °C (400 °F). Place the cherry tomatoes and garlic slices on a baking sheet covered with aluminum foil. Drizzle with a little olive oil and season to taste with oregano, salt and pepper.
Roast for 20 minutes in the oven. During the last 12 minutes, add the duck legs confit and continue roasting.
In the meantime, cook the pasta al dente according to package directions, and drain into a colander. Return the pasta to the saucepan and drizzle with olive oil. Season with salt and pepper to taste, then add the feta cheese and green onions. Mix and set aside.
Remove the baking sheet from the oven and separate the meat from the duck legs. Break the meat up into small pieces and add to the pasta. Mix, then add the roasted tomatoes and garlic. Stir gently to combine and serve immediately.