Preheat your oven to 425°F (220°C). Line the baking sheet with parchment paper for easier cleanup (optional).
Peel the sweet potatoes and cut them into 1-inch cubes. Place the cubes in a large mixing bowl.
Drizzle the olive oil over the sweet potatoes. Sprinkle with salt, black pepper, and ground cinnamon if using. Toss until the sweet potatoes are evenly coated.
Spread the sweet potatoes in a single layer on the prepared baking sheet. Make sure there's space between the pieces to allow for even roasting.
Roast in the oven for 25-30 minutes, stirring halfway through, until the sweet potatoes are golden brown and tender.
While the sweet potatoes are roasting, toast the chopped walnuts in a small saucepan over low heat for about 5 minutes, stirring frequently, until fragrant. Be careful not to burn them.
After the sweet potatoes are done, remove them from the oven and let them cool slightly. Drizzle the warm maple syrup over the roasted sweet potatoes and gently toss.
Transfer the sweet potatoes to a serving dish and sprinkle the toasted walnuts and crumbled goat cheese on top.
Garnish with fresh parsley if desired, and serve warm.