Preheat your oven to 425°F.
Trim any excess fat from the beef and pat dry. Season it generously with salt, pepper, chopped rosemary, and thyme.
Peel and cut the carrot and parsnip into sticks or bite-sized pieces. Slice the red onion into wedges.
In a bowl, toss the vegetables with olive oil, salt, pepper, and a little extra chopped rosemary and thyme.
Spread the vegetables on a baking sheet in a single layer. Roast them in the preheated oven for 20 minutes until they start to get tender and crispy.
Meanwhile, heat an oven-safe skillet over medium-high heat. Sear the beef on all sides until nicely browned, about 2-3 minutes per side.
Transfer the skillet with the beef into the oven and roast along with the vegetables for an additional 10-15 minutes, or until the beef reaches your desired level of doneness (aim for medium-rare to medium).
Remove the skillet and vegetables from the oven. Let the beef rest for 5 minutes before slicing.
Plate the sliced beef alongside the roasted root vegetables and serve immediately.