Plays an essential role in the viral genome replication. Participates, together with NSP2, in the formation of viral factories (viroplasms) which are large inclusions in the host cytoplasm where replication intermediates are assembled and viral RNA replication takes place. Orchestrates the recruitment of viroplasmic proteins such as capsid proteins to these factories. Homodimer. Interacts with VP1. Interacts with VP2. Interacts with NSP2; this interaction leads to up-regulation of NSP5 hyperphosphorylation and formation of virus factories. Interacts with NSP6. Found in spherical cytoplasmic structures, called virus factories, that appear early after infection and are the site of viral replication and packaging. O-glycosylated. Hyperphosphorylated on serine residues, when in dimeric form. Phosphorylation by host CK1 is required for the hyperphosphorylation of NSP5 dimer. Belongs to the rotavirus NSP5 family.