Major structural component of the ciliary rootlet, a cytoskeletal-like structure in ciliated cells which originates from the basal body at the proximal end of a cilium and extends proximally toward the cell nucleus (By similarity). Furthermore, is required for the correct positioning of the cilium basal body relative to the cell nucleus, to allow for ciliogenesis (PubMed:27623382). Contributes to centrosome cohesion before mitosis (PubMed:16203858). Homomer. Interacts with KLC3, NEK2 and the N-terminus of CEP250. Interacts with CEP44 (PubMed:31974111). In ciliated cells, associated with ciliary rootlets. In non-ciliated cells, localized between, around and at the proximal ends of the centrioles. Dissociates from the centrioles at the onset of mitosis and reassociates with them at anaphase. Phosphorylated by NEK2 which may regulate its association with centrosomes. Belongs to the rootletin family.