Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Trim any excess fat from the sirloin tip beef and cut it into uniform 1-inch cubes.
Wash and dice the red potatoes into 1/2-inch pieces, leaving the skins on for added texture and fiber.
Mince the garlic cloves and finely chop the fresh rosemary and thyme leaves.
In a large mixing bowl, combine the beef cubes, diced potatoes, minced garlic, chopped herbs, sea salt, and black pepper.
Drizzle the olive oil over the mixture and toss thoroughly until every piece is evenly coated in oil and seasonings.
Spread the beef and potatoes in a single layer on the prepared baking sheet, ensuring they are not crowded so they roast rather than steam.
Roast for 20-25 minutes, tossing the ingredients halfway through, until the potatoes are tender and the beef is cooked to your preference.
Remove from the oven and let the beef rest on the pan for 5 minutes to allow the juices to redistribute before serving.