how long to cook roast beef at 350
Answer   If frozen then a 4 lb. beef roast will cook faster. Put the oven up to 400 (lid on roaster) for 20 - 30 minutes and sear, then put the temperature down to â¦ 350 and cook 15 minutes per pound.   If the 4 lb. beef roast is thawed then sear as above and cook for 20 minutes per pound.ow long you would cook a 2.2 pound beef roast depends upon how you  like it cooked. For a rare beef roast, cook at 200 degrees  Celsius/390 degrees Fahrenheit for 30 minute â¦ s. For a medium beef  roast, cook for 45 minutes or for well done meat, cook for an hour.