Place the tri-tip in a shallow baking dish or on a plate and rub with the olive oil. Rub with the salt, pepper, coffee and garlic cloves until the seasonings are evenly coating the surface of the meat. Transfer to a sealable plastic bag and seal, squeezing out as much air as possible. Refrigerate for at least 2 hours or up to overnight.

If using a charcoal grill, light one chimney full of charcoal. When all of the charcoal is covered with gray ash, pour out the coals and arrange them on one side of the charcoal grate. If using a gas grill, set half the burners to the highest heat setting, cover and preheat for 10 to 15 minutes. Clean and oil the grill grate.

Remove the tri-tip from the bag and place directly over the hot side of the grill. Top the tri-tip with the rosemary sprigs and cook, turning frequently, until the meat is well charred and an instant-read thermometer inserted into the thickest part of the meat registers 125°F for medium-rare or 130°F for medium, about 12 minutes total. Transfer the tri-tip to a cutting board, tent with aluminum foil and let rest for 5 minutes. Season with additional salt, slice the meat against the grain and serve.

Alternatively, to cook the tri-tip indoors, in a large stainless-steel or cast-iron fry pan over high heat, warm the vegetable oil until shimmering. Remove the tri-tip from the bag and season with salt. Add the tri-tip to the pan and cook, turning frequently, until an instant-read thermometer inserted into the thickest part of the meat  registers 125°F for medium-rare or 130°F for medium, reducing the heat as needed if the meat smokes excessively or starts to burn. Transfer the tri-tip to a wire rack set over a rimmed baking sheet and let rest for 5 to 10 minutes. Transfer to a cutting board, slice the meat against the grain and serve.