The soils of the Roero are alluvial in origin and contain a significant amount of sand. This is younger land than is found in the Langhe where the hills remained beneath the sea until approximately 2 and a half million years ago. Evidence can be seen in rock faces formed of different coloured layers and the presence of many fossils.The main component of the Roero’s soils is sandstone, a sedimentary rock of marine origin made up of marl and sand with substantial levels of chalk and clay; this leaves the ground relatively soft and permeable.
The soils of communes Monticello, Piobesi, Castagnito and Castellinaldo are characterised by blue-grey, sandy clays and marls layered with sandstone, while to the west of Corneliano and Vezza d’Alba yellow sand, similar to that found around Asti, predominates and is interspersed with marl and gravel.
Finally north of Montà we find even younger land where sand mixes with clay.
The land given over to viticulture in the Roero is relatively poor in organic matter but contains a significant proportion of chalk and is quite rich in phosphorus and potassium.
The calcium content divides the area in two: the first, to the north-northwest, has very little chalk and is covered in broad-leaved forests, the second, to the south-southeast, registers between 5 and 10% chalk and includes land used for agricultural purposes.