Preheat your oven to 225°F (110°C). Position a rack in the center of the oven.
In a small bowl, combine the kosher salt, black pepper, garlic powder, onion powder, dried oregano, dried rosemary, and smoked paprika. Mix well to create your spice rub.
Pat the tri tip roast dry with paper towels. This helps the spice rub adhere better and promotes better browning.
Drizzle the olive oil over all sides of the tri tip and massage it into the meat.
Apply the spice rub liberally to all sides of the tri tip, pressing gently to ensure it adheres well. Be sure to cover the entire surface of the meat.
Place a wire rack on a rimmed baking sheet or roasting pan. Position the seasoned tri tip fat side up on the rack.
Insert a meat thermometer into the thickest part of the roast if using an oven-safe thermometer.
Transfer the tri tip to the preheated oven and roast slowly until it reaches an internal temperature of 130°F (54°C) for medium-rare or 135°F (57°C) for medium, approximately 1 hour and 30-40 minutes depending on size.
Once the desired internal temperature is reached, remove the tri tip from the oven and tent loosely with aluminum foil. Let it rest for 15-20 minutes. This crucial step allows the juices to redistribute throughout the meat.
After resting, transfer the tri tip to a cutting board. Identify the grain of the meat (the direction of the muscle fibers) and slice against the grain into thin, ¼-inch thick slices for maximum tenderness.
Arrange the slices on a serving platter and serve immediately, drizzling with any accumulated juices from the cutting board.