For example, I found a blog history here at http://www.angelfire.com/rock3/yardbird_sect/secthistory2.html of a band called Downliner's Sect, which Rod joined in 1981. The article implies that he might had continued playing with the band for a few years, but doesn't say when he left the band. It goes on to say that by the late 80's Rod had "disappeared" and was presumed dead.
For years throughout the late 90's and 2000's, I would occasionally do a search to see if there was any new info on Rod De'Ath. In 2008, I found it here at http://www.wordmagazine.co.uk/content/valley-shadow-de039ath#.
Here's an interview with Rod at http://www.roryon.com/rod211.html that was apparently done in 1996. Since then, I've been able to find out nothing on what has happened to Rod in the intervening 13 years.
Along with playing with Downliner's Sect, he also did a couple of albums with his former Rory bandmate Lou Martin in a band called Ramrod. He also arranged a Screamin' Lord Sutch album. At some point he moved to America, living in New York City and got married and had a child.
According to these articles and interviews, Rod had then some sort of accident in which he lost an eye, was in an extended coma and suffered total memory loss. As of the interview of 1996, he said he had regained 95% of his memory.
This page http://www.ridingshotgun.co.uk/authors.html talks about a book by Gerry McAvoy, longtime bassist for Rory.