Place diced sweet potatoes on a large rimmed baking sheet. Drizzle with olive oil and season with salt and pepper; toss to coat. Roast in the oven until tender, about 20-30 minutes. Remove from the oven; set aside to cool.
Meanwhile, bring a large pot of water to a boil. Cook pasta according to the package directions for al dente. Drain and set aside to cool.
Place cooled pasta in a large bowl. Add the roasted sweet potatoes, broccoli, red onion, cranberries, and pecans. Gently toss with poppy seed dressing. Cover and refrigerate for at least an hour.
Stir just before serving, adding more dressing if needed. Top with crumbled goat cheese.