Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Dice the yellow potatoes into half-inch cubes and toss them on the baking sheet with half of the olive oil and a pinch of salt and pepper.
Roast the potatoes for 20 to 25 minutes, tossing halfway through, until they are golden and crispy on the outside.
While the potatoes roast, finely mince the garlic and combine it in a small bowl with the rosemary, thyme, and the remaining salt and pepper.
Pat the sirloin steak dry with a paper towel and rub the herb and garlic mixture firmly into both sides of the meat.
Heat the remaining olive oil in a cast-iron skillet over medium-high heat until the pan is shimmering and hot.
Place the steak in the skillet and sear for 4 to 5 minutes per side for a perfect medium-rare finish.
Add the trimmed asparagus spears to the baking sheet with the potatoes during the last 8 minutes of roasting time.
Remove the steak from the skillet and let it rest on a cutting board for at least 5 minutes to lock in the juices.
Slice the steak against the grain and serve it alongside the roasted potatoes and tender asparagus.