It's an isopod. I'm not willing to guess more than that without knowing your location, the kind of environment in which it was found, and the size.

Thank you, it was found in a house in a suburb outside of Chicago, IL.

Commonly called pillbug, when disturbed, it rolls into a ball, or pill. I can't tell which species of genus Armadillidium it is.

From bugguide:
A. vulgare,... rolls into a perfect ball, while the tail of A. nasatum, ... sticks out when it rolls into an imperfect ball.

Thank you! I've seen those pillbugs. Very interesting.