Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Peel and dice the sweet potato into 1/2-inch cubes, then toss them on the baking sheet with 0.5 tsp of olive oil and a pinch of salt.
Roast the sweet potatoes for 15 minutes to give them a head start on caramelization.
Remove the sheet from the oven and add the broccoli, bell peppers, and zucchini, tossing them with another 0.5 tsp of olive oil.
Return the vegetables to the oven and roast for an additional 12-15 minutes until the edges are golden and tender.
While the vegetables finish, season the steak generously on both sides with sea salt and black pepper.
Heat the remaining 0.5 tsp of olive oil in a cast-iron skillet over medium-high heat until shimmering.
Sear the steak for 3-5 minutes per side for medium-rare, adding the minced garlic and rosemary to the pan during the final 2 minutes of cooking.
Transfer the steak to a cutting board and let it rest for 5 minutes to lock in the juices before slicing against the grain.
Plate the sliced steak alongside the roasted sweet potatoes and mixed vegetables, drizzling any remaining pan juices over the meat.