Preheat oven to 425F

Scrub sweet potatoes and cut into 1-inch wedges

On a rimmed baking sheet, toss sweet potatoes with 1 tbsp (for 4 servings; scale up) olive oil and season with salt and pepper. Spread in an even layer; (roast about 45 min before serving) roast, turning once after 25 min, until golden and tender. Let cool slightly.

Meanwhile, pulse parsley, garlic, walnuts, zest, and lemon juice in a food processor until coarsely chopped. Add remaining oil in a steady stream and process until combined. Season with salt and pepper.

To serve, drizzle some pesto over sweet potatoes, and serve the rest of the pesto next to it.