Hello, Michael.  I have a little insider information where Mr.McGuinn, and things "Byrd" are concerned,probably stemming from my one time fanaticism with the Byrds, especially the country rock version with Clarence White, and Gene Parsons, ie post Crosby and Gene Clark, in the early 70's.  I have also seen "Roger" more recently in solo concert settings (moderately painful on the ears).  His birthname is Jim or James. His mother called him "Jimmie" (I'm not making this up), and he switched to Roger because it had more of what he felt was a good "stage" sound, or rock name...He also has a fascination with space flight, rockets etc...so perhaps he got it from saying "roger" all the time at the controls of his imaginary space ship (joking this time). 

I do know, through various reliable sources (one of the aforementioned members..I won't post which one, lives close to a friend of mine),  that the other band members of the Byrds, especially the later versions now hate him for his: 1. egotism  2. for siphoning off monies at various times (their monies) for his own indulgences including a Porsche or two, and other contraptions that some adults need for play.   Also, he is known amongst certain people in music (people who record, produce etc..),  to be a bit of a pr............i........ck.  You fill in the blanks. 

As a fan, I love what he contributed with the Byrds, that is all...I don't know, nor would offer to comment on the man personally.  

My Byrds favs are: Dr.Byrds and Mr.Hyde, The Notorious Byrd Bros, The Ballad of Easy Rider, Untitled, Byrdmaniax, Farther Along, and Sweetheart of the Rodeo.

Gene