Preheat oven to 400 degrees F. Place the sweet potato, brussels sprouts, and red onion on a large baking sheet. Drizzle with olive oil and toss. Season with salt and black pepper, to taste. Roast in the oven for 25-30 minutes, stirring occasionally. Remove from oven and set aside.
Meanwhile, brown the butter. In a small saucepan, melt the butter over medium-low heat and continue to cook, swirling occasionally, until butter turns golden brown, Skim foam from top, and remove from heat. Pour into a bowl to stop the cooking and set aside.
Bring a large pot of water to boil. When the water comes to a rolling boil, add a little salt, then add the pasta. Cook pasta to al dente, cooked through but still a little firm. When the pasta is done cooking, drain and put back in the pot.
Pour brown butter over the pasta and add the roasted vegetables. Heat over medium until heated through. Remove from heat and stir in the pecans, dried cranberries, and feta cheese. Season with salt and black pepper, to taste. Serve.