The former tiling manager faced four counts of making objectionable publications, two counts of rape of a child under 12, and a count of possession of an objectionable publication. He also sought bail on these.
Crown counsel Ben Smith said the alleged offending was "driven" and "most serious" as he opposed Williams' bail application.
"There are five complainants regarding sexual offending against children between the ages of 3 and 15," he said.
However, the fourth and fifth complainants only came to light due to the diligence of a police officer whose job it was to review the digital material seized by police at the time of the arrests of Williams and Rose, the court heard.
Smith said this was "difficult work" and it was hard to know whether more complainants might be identified from the ongoing investigation.
The police investigation into the couple has already accrued more than 150,000 recordings, including nearly 2000 videos. There are another 122,000 images and videos still to be analysed.
Williams was remanded on electronically monitored bail until his next appearance for all charges on September 22.
Rose is expected to appear again in Tauranga District Court on August 22.
Rose, jointly charged with Williams, has already denied the original charges. She appeared in Tauranga District Court last week to face nine new charges, which she is yet to enter a plea to.