Preheat your oven to 425°F (220°C).
Rinse and pat dry the beef sirloin. Season it with salt, pepper, and half of the chopped rosemary.
Cut the baby potatoes in halves and trim the asparagus, then toss both in a bowl with olive oil, minced garlic, the remaining rosemary, salt, and pepper.
Place the potatoes on a baking sheet and roast in the oven for about 20 minutes, until they start to become golden and crisp.
While the potatoes roast, heat a skillet over medium-high heat. Sear the beef on all sides until browned, about 2-3 minutes per side. Once seared, transfer the beef to another baking tray.
Add the asparagus to the baking sheet during the last 10 minutes of the potatoes' roasting time, ensuring they remain tender yet crisp.
Place the beef in the oven along with the vegetables and roast for an additional 8-10 minutes, or until the desired level of doneness is reached.
Remove from the oven and let the beef rest for a few minutes before slicing. Serve with the crispy potatoes and tender asparagus.