Most of y'all are aware of Brian Kernighan's troff involvement. My understanding is that he pretty much took over nroff/troff after Joe Ossana died, and came out with ditroff.

But Brian had much earlier involvement with non-UNIX *roff.  When he was pursuing his PhD at Princeton, he spent a summer at MIT using CTSS and RUNOFF.  When he came back to P'ton, he wrote a ROFF for the IBM 7094, later translated to the IBM 360.  Many generations of students, myself included, use the IBM ROFF (batch, not interactive) as a much friendlier alternative to dumb typewriters.  I don't know if 360 ROFF spread beyond Princeton, but I wouldn't be surprised.

BTW, during my summer at Bell, nroff/troff was one of the few programs I could not port to the Interdata 8/32 - it was just a mess of essentially typeless code.  I don't think Joe Ossana got around to it either before he died.