The common pillbug doesn't have the appendages and are capable of rolling into a tight ball. They are often called "rolly-polies". Pillbugs and Sowbugs (oval and dark gray)are more closely related to shrimp and crayfish than to insects being of the class Crustacea. The typical sowbug has two tail-lole appendages at the tip of the abdomen. Sowbugs are incapable of rolling into a tight ball.
More information for prevention, identification and control: Pillbugs and Sowbugs