I don't have enough information to specifically say who Roman Coleman is in this 'true story'. It could be an ordinary person with a unique experience, or perhaps someone who has made an impact in a particular field but is not widely known outside of the context of this story.
I'm not sure who Trevor Holt specifically is in this story without more context. It could be a fictional character created for a particular book, movie, or other form of media.
Well, Coleman science fiction might often feature advanced technological concepts. It could have unique alien species with their own cultures. For example, the stories might explore the implications of time travel or faster - than - light travel.
I'm not sure specifically as I haven't read it. It could be about a place called Coleman Hill and the events, characters, and stories that unfold there.