Rollers are employed to level ploughed earth - they serve to reconsolidate (compress) overly loose soil and to crush coarse clods. This is particularly important, because such a subsoil is required for the smooth functioning of harvesting machines. Formerly rollers were constructed from wood and stone, though since the end of the the 19th Century they are almost exclusively made of iron.
Alongside crushing and compacting they often have the important function of depth control for tilling machines, as they always roll away the surface layer of the soil. Rollers are effective on the one hand due to their substantial weight, on the other due to their profile shape. In this respect, a distinction is made between smooth and coarse rollers. Smooth rollers are primarily utilized in the leveling of pastureland. In contrast, coarse rollers are used to break up the surface of firm earth/soil.