Cooking a 5 pound pork sirloin roast
The only way to tell if a pork roast has been cooked long enough is by taking an internal temperature with an instant-read thermometer in several places around the thickest portion of the roast.

The National Pork Board recommends cooking pork chops, roasts, and tenderloin to an internal temperature between 145° F. (medium rare) and 160° F. (medium), followed by a 3 minute rest. Since large cuts increase approximately 10° F while resting, remove them from the heat at 150° F. followed by a 10 minute rest.
Pork Cooking Times and Temperatures