I can't answer your question about Rozier. I used to like Bill Simmon's stuff on ESPN and even bought his basketball encyclopedia book when it was published a few years ago.
Seems he has gotten less interesting to me since he moved to LA. His HBO TV show was a massive bust. His podcast can sometimes be good but he talks way too much about gambling for my taste - I don't bet on sports except for a few bucks with friends a couple times a year.
I do think he is wired into the Celtics so there probably is some truth to the Rozier rumors.
Maybe I haven't forgiven him for dogging my Clippers all the time - even after he bought season tickets to their games a couple years back.
I haven't really followed him, he talks too much even about Celtics stuffs. I could not even finish his interview with Bill Russell.