Their armour is made of an extremely strong metal. They curl into balls, to protect themselves, and to roll into enemies as an attack and across the terrain as a form of locomotion.In-game description
The Rolmar is the Stage 3 power-balanced form of the Horizon group.
Rolmars were removed from the game before it was released, so although their data still exists, they do not appear anywhere.
A Rolmar should evolve from Shakasi, but it is disabled in the alpha version. It does not evolve again.