Participates in replication and packaging of the viral genome. Plays a crucial role, together with NSP5, in the formation of virus factories (viroplasms) which are large inclusions in the host cytoplasm where replication intermediates are assembled and viral RNA replication takes place. Displays ssRNA binding, NTPase, RNA triphosphatase (RTPase) and ATP-independent helix-unwinding activities. The unwinding activity may prepare and organize plus-strand RNAs for packaging and replication by removing interfering secondary structures. The RTPase activity plays a role in the removal of the gamma-phosphate from the rotavirus RNA minus strands of dsRNA genome segments. Homooctamer. Interacts with VP1; this interaction is weak. Interacts with NSP5; this interaction leads to up-regulation of NSP5 phosphorylation and formation of viral factories. Found in spherical cytoplasmic structures, called viral factories, that appear early after infection and are the site of viral replication and packaging. Belongs to the rotavirus NSP2 family.