Preheat oven to 400 °F (200 °C)
Toss diced potatoes with olive oil, salt and pepper
Spread potatoes in a single layer on a baking tray
Roast until edges are golden and crispy
While potatoes roast, heat a skillet over medium heat
Add ground beef and cook until no pink remains
Sprinkle taco seasoning over beef
Add water and simmer until mixture thickens
Divide crispy potatoes into serving bowls
Top each bowl with seasoned beef
Sprinkle shredded cheddar over hot ingredients
Add sour cream, tomatoes, green onions and olives
Drizzle with taco sauce or salsa
Serve immediately