Heat oven to 425°F. Rub roast with oil, salt and pepper and sear in an ovenproof heavy skillet over medium-high heat for 2 to 3 minutes on each broad side.
Add 1/2 cup of the measured stock around the beef and move the uncovered skillet to the oven. Roast for 35 to 50 minutes until the center reaches 145°F, checking early and adding a small amount from the reserved stock if the pan threatens to dry.
Transfer beef to a board and rest for 10 minutes. Pour the pan liquid into a heatproof cup, skim excess fat and leave 1 tablespoon of the fat in the skillet.
Cook shallots in the reserved fat over medium heat for 3 minutes. Add wine, scrape up the browned bits and simmer for 2 minutes, then add skimmed pan juices, remaining measured stock and thyme.
Simmer for 10 to 15 minutes until the jus tastes concentrated, then strain and skim again if needed. Aim for about 2 cups for dipping, reducing a little longer if the flavor is weak.
Split rolls, butter the cut faces and toast under the broiler for 1 to 2 minutes. Slice rested beef very thinly across the grain and divide among the rolls.
Close the sandwiches and serve one per person with about 1/2 cup hot jus in a small dipping cup. Dip each bite just before eating rather than soaking the whole sandwich in advance.