To develop, plants need water, light, carbon, oxygen and mineral elements. Fertilisers contain feed elements which nourish plants. Soil conditioners are designed to improve the qualities of the soil, they include basic and organic soil conditioners.
Since its creation, the Roullier Group has been using a coralliferous seaweed as a natural component of many fertilisers. It gives preference to the use of mineral or plant raw materials which respond to the concern of sustainable agriculture : lithothamne, natural soft phosphates, potassic extracts of plant origin, etc.

Raw materials used in fertilisation:
- Nitrogen (N): a necessary element in plant feed. It enters into the constitution of amino acids and proteins which ensure the yield and quality of harvests.
- Phosphor (P): element necessary for plant growth. It participates in most of the biochemical activities of plants.
- Potash (K).
- Lithothamne (or maërl) contributes to improving the properties of soil and optimises the environment of micro flora.
- Trace elements make it possible to fight against deficiencies related to crop practices.

Since its origin, among farmers, the Group has been highlighting the value of the "precision fertilisation" approach: to provide the precise amount of fertiliser to the plant at the correct stage of its growth cycle. Always a step ahead, the Roullier Group is developing the notion of "programmed fertilisation", by perfecting products with elements which are valorised by the plant, according to the vegetative stages and the need.