Question: how long does it take to cook a 2 1/2 pound roast beef?
Answer: Preheat oven to 375 degrees F (190 degrees C). If roast is untied, tie at 3 inch intervals with cotton twine. Place roast in pan, and season with salt, garlic powder, and pepper. ... 
Roast in oven for 60 minutes (20 minutes per pound). Remove from oven, cover loosely with foil, and let rest for 15 to 20 minutes.