Preheat oven to 420°F (or air fryer to 400°). Scrub potatoes with brush under cool water. Peel potatoes, reserve skins for air fryer potato skins (see post), or discard. Dice potatoes into 1" cubes. Put in bowl.
Drizzle olive oil over potatoes. Toss to coat. Sprinkle on Harissa. Measure with your heart. If harissa doesn't contain salt, sprinkle with desired amount of salt. Toss.
Place sweet potatoes on sprayed baking sheet. Spread out so they don't touch. Use 2 pans if you have to, to not overcrowd.
Roast for 15-18 minutes, until golden brown. Remove from oven. Squeeze half lemon over the top of the potatoes. Stir and sprinkle with salt, if desired. Enjoy.
Notes
If you like a spicier side dish, add more harissa. Make sure to not overcrowd the pan. Use 2 pans if need be.