This is a type of shape called a "two circle roller." It's a mathematical shape that, when it rolls, every point on its surface touches the ground. Anyway, wikipedia does a better job of describing it...

https://en.wikipedia.org/wiki/Oloid

Print TWO halves and glue them together.

An openSCAD file is also included if you want to experiment.

Not my video, but a nice animation of how an oloid rolls: https://www.youtube.com/watch?v=GUyou2QelRo

Edit: My father-in-law corrected me that this shape is not an oloid. He is technically correct. (The very best kind of correct!) The two-circle roller is a shape only related to the oloid. This author deeply regrets the error.