Imagine standing in your living room among a group of your friends. Your Jack Russell Terrier is in the center of the room, staring at you eagerly, waiting for your next command. You tell him to "roll over" and he drops to the floor, and flips over, then jumps back up again, smiling at the crowd, clearly enjoying all of the attention and treats.
That might seem like a simple, easy thing to imagine, but that is exactly the point. Teaching your dog to roll over is very attainable. It is adorable, fun, and provides a great foundation for other tricks like 'play dead' and rolling up into a blanket.