Roll crimp is designed for use with heavy recoiling revolver cartridges. To seat bullets without crimping, simply unscrew the die until the crimp ring no longer engages the case mouth.
Roll Crimp Seater Die
Plastic storage case
A Bullet Seater is used to push (seat) the bullet down into the case to a specific depth and is found in the Seating die.
As the seater pushes the bullet into the case, the shoulder of the die crimps the case against the bullet.