Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Peel the sweet potato and cut it into 1/2-inch cubes, then toss them on the baking sheet with 1 teaspoon of olive oil and a pinch of sea salt.
Roast the sweet potatoes for 15 minutes, then add the trimmed green beans to the same tray, tossing to coat, and roast for another 10 to 12 minutes until tender.
While the vegetables roast, pat the steak dry with a paper towel and season both sides evenly with sea salt and black pepper.
Heat the remaining 1 teaspoon of olive oil in a cast-iron skillet over medium-high heat until the oil is shimmering.
Place the steak in the hot skillet and sear for 4-5 minutes per side for medium-rare, or until it reaches your desired level of doneness.
During the last 2 minutes of searing, add the minced garlic and finely chopped rosemary to the pan, tilting the skillet to spoon the aromatic oil over the steak.
Remove the steak from the heat and let it rest on a cutting board for 5 minutes before slicing against the grain to serve with the roasted vegetables.