Place sweet potatoes in a bowl. Drizzle with oil, then add chili powder, cumin, garlic powder, cumin, lime juice, and salt and pepper to taste. Toss to coat well. Transfer to a skillet and saute over medium-high heat for 6-8 minutes until easily pierced with a fork.
Stir together all ingredients for the corn salsa.
Assemble burrito bowls by placing tortillas in the bottom of four bowls. Add rice, black beans, corn salsa, sweet potatoes, and guacamole. Serve immediately.