Step 1: Preheat the Oven
Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper or lightly grease it with olive oil.

Step 2: Prepare the Sweet Potatoes
Peel and cut the sweet potatoes into 1-inch cubes. Place them in a large mixing bowl, drizzle with olive oil, and sprinkle with salt, black pepper, smoked paprika, and cinnamon (if using). Toss well to coat each piece evenly.

Step 3: Arrange Sweet Potatoes on Baking Sheet
Spread the seasoned sweet potatoes evenly on the prepared baking sheet in a single layer. Ensure there’s enough space between the pieces so they can roast evenly. Avoid overcrowding, which can lead to steaming rather than roasting.

Step 4: Roast the Sweet Potatoes
Roast in the preheated oven for about 25-30 minutes, stirring halfway through the cooking time to ensure even browning. The sweet potatoes should be fork-tender and slightly caramelized around the edges.

Step 5: Prepare the Garlic Herb Butter
While the sweet potatoes are roasting, prepare the garlic herb butter. In a small saucepan over medium heat, melt the butter. Add minced garlic, rosemary, thyme, and parsley. Stir frequently for 2-3 minutes, until the garlic is fragrant. Remove from heat and stir in salt, pepper, and lemon juice (if using).

Step 6: Combine and Serve
Once the sweet potatoes are done roasting, remove them from the oven. Drizzle the garlic herb butter over the roasted sweet potatoes and gently toss to combine. Transfer to a serving dish and garnish with a bit more fresh parsley if desired.