Pat the sirloin tip roast dry
Season all sides with salt, pepper, and optional garlic powder, onion powder, or rosemary
Let the roast sit at room temperature for 30 to 60 minutes
Preheat the oven to 450°F
Place the roast on a rack in a roasting pan
Roast at 450°F for 15 minutes
Reduce the oven temperature to 325°F
Continue roasting until the internal temperature reaches 130°F to 135°F for medium-rare or 140°F to 145°F for medium
Check the temperature with a meat thermometer inserted into the thickest part
Remove the roast from the oven
Tent loosely with foil
Rest for 15 to 20 minutes
Slice thinly against the grain
Serve immediately