I have three. The oldest one is a dowel that's about 2 inches in diameter and probably about 16 inches long. The one I use most is 4= inches in diameter, has ball bearings and handles. Let me tell you, you don't have to work very hard with this Big Daddy!
The third is a small one I carry with me on jobs that is great for rolling out already prepped puff pastry and the like.. about 6 inches long and just about 1 inch in diameter.
and then there's the pizza dough roller.