Choosing the correct roller:
When applying grounds to a plate it is advisable to select a more economical roller as the ground is very quick to damage the rubber. A soft roller is also suggested

In viscosity printing various rollers of different hardnesses are recommended

For relief printing you may use either a hard or soft roller, each one will give a different result. The softer the roller the more sub level detail will be picked up. By using a hard roller you will produce a crisper image.