Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Scrub the potato and dice it into small, uniform half-inch cubes to ensure they get extra crispy.
Toss the potato cubes on the baking sheet with half of the avocado oil, a pinch of sea salt, and black pepper.
Roast the potatoes in the oven for 15 minutes while you prep the remaining ingredients.
Season the beef sirloin on all sides with the dried rosemary, garlic powder, and the remaining sea salt and pepper.
Remove the baking sheet from the oven, push the potatoes to one side, and place the beef and trimmed green beans on the other side.
Drizzle the remaining avocado oil over the green beans and return the sheet to the oven.
Roast for 12 to 15 minutes or until the beef reaches an internal temperature of 145°F for medium-rare and the potatoes are golden brown.
Let the beef rest for 5 minutes before slicing against the grain and garnishing with fresh parsley.