He looks like Roy but has a Modelatrix symbol on his belly, his eyes are not connected to his forehead and his shells are hexagon shaped, not to mention a black stripe going down his belly and his palms being flat.
He can roll into enemies by rolling into a sphere.
His shells deflect everything and make him survive Magma/Acid and drops from space.
Spinball is subjected to the physical laws of reflection and conservation of momentum, meaning that he has difficulty stopping or controlling his direction if he picks up speed. Also, if Spinball is on a very sticky surface, he can't get up.