Stir together hoisin, ginger, garlic, vinegar, soy sauce, and pepper until well blended. Rub marinade all over roast, coating it well. Place in a glass baking dish, cover, and allow to marinate in the refrigerator at least 8 hours, but preferably overnight.
Remove tri-tip from the refrigerator and let it sit at room temperature for 30 minutes. Heat the oven to 375°F. Blot roast dry with paper towels to remove some of the excess marinade.
Heat olive oil in a large frying pan over medium-high heat. Sear roast for about 2 minutes per side or until nicely browned. Transfer roast to a small roasting pan or baking dish and place in the oven. Cook until it reaches an internal temperature of 125°F for medium rare, about 20 to 22 minutes.
Remove roast from the oven and cover loosely with foil. Let rest for 15 minutes before carving. Slice across the grain and serve.
Beverage pairing:Torbreck Woodcutters Shiraz, Australia. The hoisin, ginger, and soy give the beef a sweetness and spiciness that is best matched by a wine that also has both. Australian Shiraz is such a wine, and this one has a plump core of sweet blueberry fruit that is appropriately undercut with pepper and spice.