Step 1. Preheat the oven to 450 degrees. Tie roast with kitchen string in three evenly spaced places to maintain its shape.
Step 2. In a small bowl, whisk together 1 tbls oil, the mustard, oregano, both chili powders, cumin, pepper and garlic.
Step 3. In a large skillet, heat remaining oil until very hot. Season beef all over with salt. Place it in the pan and sear bottom without movig it until it forms a golden brown crust, about 3-4 mins. Turn and repeat with remaining sides.
Step 4. Transfer beef to a rimmed baking sheet. Using a pastry brush, smear the mustard-chili rub all over the beef. Roast until a meat thermometer registers 115 degrees for rare or 120 degrees for medium rare. Remove from oven and let rest 15 mins. Slice and serve or, if desired, let beef completely cool, then wrap and refrigerate. Remove and bring to room temperature at least 2 hrs before slicing and serving.