Preheat your pellet smoker to 250°F.
Trim any excess fat from the top sirloin roast, leaving a thin layer.
Rub the entire surface of the roast with olive oil, ensuring that it is coated evenly.
Combine the kosher salt, black pepper, garlic powder, onion powder, and smoked paprika in a small bowl.
Sprinkle the seasoning mixture over the entire surface of the roast, ensuring that it is evenly coated.
Place the seasoned top sirloin roast on the smoker grates and close the lid.
Smoke the roast for 2 1/2 to 3 hours, or until it reaches an internal temperature of 135°F.
Once the roast has reached the desired internal temperature, remove it from the smoker and let it rest for at least 10 minutes.
Slice the smoked top sirloin roast against the grain into 1/2-inch slices and serve.