Preheat oven to 400°F (204°C).
Toss cubed sweet potatoes with 1 tablespoon olive oil, smoked paprika, garlic powder, salt, and pepper on a large rimmed baking sheet.
Roast sweet potatoes for 25 to 30 minutes, tossing once halfway through, until tender and caramelized.
In a large skillet, heat the remaining 1 tablespoon olive oil over medium-high heat.
Add the ground beef and red onion; cook for 8 to 10 minutes while breaking into small crumbles until beef is fully browned and onion is translucent.
Stir in the diced bell pepper and cook for an additional 3 to 4 minutes.
Add the baby spinach to the skillet and stir for 1 to 2 minutes until just wilted.
Remove skillet from heat and adjust seasoning with additional salt and pepper if desired.
Divide the roasted sweet potatoes and the beef mixture evenly into four serving bowls.
Garnish each bowl with fresh avocado slices before serving.