Chuck, brisket and round cuts are best for creating roast beef. Typically, roast beef should be cooked slowly, and as such, a beef roast should be a tougher cut of meat.
When cooking roast beef, the time and temperature are key to the cooking process. Roast beef is basically a braise that cooks for a long period of time at a lower temperature. Tough, lean cuts with a lot of connective tissue but little fat that see a lot of movement on the animal are tough to chew if grilled or seared quickly, but when cooked properly, the collagen breaks down into gelatin, which tenderizes the meat. This makes the meat succulent, and adds richness and body into the braising liquid, subsequently turning that liquid into sauce.
The chuck comes from the front of the animal. When shopping for chuck beef, look for shoulder steak, chuck roast, boneless chuck roast, beef chuck arm, or chuck shoulder pot roast. The brisket is from the breast or lower chest of the animal and has long strands of meat. The flat cut is lean, the point cut has more fat, and a brisket is best cut against the grain of the meat. The round cut is from the rear of the animal.