Take the roast out of the fridge 30 minutes before cooking. Preheat the oven to 350°F.
Pat the roast dry. Mix the oil, garlic, salt, pepper, thyme and rosemary and rub the mixture all over the roast.
Place the roast on a rack in a roasting pan, or on a bed of thick onion slices in a baking dish.
Roast for 50–70 minutes, checking early, until a thermometer in the center reads 130–135°F for medium-rare or 140–145°F for medium.
Tent loosely with foil and rest for 15 minutes.
Slice thinly against the grain and serve with the pan juices.