Preheat oven to 425°F and line a rimmed baking sheet with parchment paper.
Peel the sweet potatoes and cut into uniform ¾-inch cubes.
In a large bowl, toss the cubes with olive oil, harissa paste, cinnamon, salt, and pepper until evenly coated.
Spread the cubes in a single layer on the prepared sheet pan, leaving space between pieces. Roast for 20 minutes.
Remove the pan, drizzle with half the honey (about 1½ tablespoons), and toss to recoat. Return to the oven and roast another 12–15 minutes, until fork-tender and caramelized at the edges.
Remove from the oven, drizzle with the remaining honey while still hot, and sprinkle with feta and parsley. Serve warm.