Preheat the oven to 375 degrees F. Line a rimmed baking sheet with parchment paper.
Peel the sweet potatoes and cut them into 1/2-inch thick wedges.
Put the potatoes in a large bowl and drizzle with the oil. Season with salt, pepper and your choice of other spices, if using, and toss to coat. Arrange the potatoes in a single layer on the prepared baking sheet.
Roast the potatoes, flipping once if their bottoms darken quickly, until tender and crispy, about 20 minutes, depending on their size. Serve with ketchup and/or ranch, if desired.