Preheat the broiler. Cut the potatoes into long noodles using a spiralizer (or use 1 pound store-bought sweet potato noodles). Spread on a rimmed baking sheet, drizzle with 2 tablespoons vegetable oil and sprinkle with 1/2 teaspoon salt and a few grinds of pepper. Broil until browned in spots and slightly softened, 3 to 5 minutes.
Heat the remaining 2 tablespoons vegetable oil in a large nonstick skillet over medium-high heat. Add the red onion, bell pepper and serrano; cook, stirring, until just softened, about 3 minutes. Add the corn, garlic, cumin, chili powder, coriander, 1/2 teaspoon salt and a few grinds of pepper. Cook, stirring occasionally, until the vegetables are tender, 3 to 5 more minutes.
Add the broiled sweet potato noodles and 1/4 cup water to the skillet with the vegetables. Cook, gently tossing, until the noodles are coated and tender, 1 to 2 minutes. Remove from the heat and stir in the cilantro and lime juice; season with salt and pepper. Serve with lime wedges.