In a skillet over medium heat, cook the ground beef until browned, about 5-7 minutes. Drain any excess fat.
Add the taco seasoning to the beef along with 2/3 cup of water. Stir and let simmer for about 5 minutes until thickened. Remove from heat and let cool slightly.
Lay a tortilla flat on a clean surface. Spread a thin layer of sour cream over the entire tortilla.
Spoon a portion of the seasoned beef onto the center of the tortilla, then sprinkle with cheddar cheese, lettuce, diced tomato, black olives, and green onions if using.
Starting from one end, roll the tortilla tightly around the filling. Repeat with the remaining tortillas and filling.
Once all tortillas are rolled, slice each roll-up into 1-inch pieces. Arrange on a platter and serve with salsa on the side for dipping.
For best flavor, chill the roll-ups in the refrigerator for at least 30 minutes before serving.