Hi,
Yes, Rollie was my grandfather. It's nice to know you appreciate his work. He was always very proud of his work with Chaplin.
I don't think the omission in MA is terribly surprising. None of the 'early bunch' got much mention. I would suspect that Chaplin didn't think there would be as much interest in them on the part of the public as the others he did talk about. Besides, Chaplin was always reluctant to 'reveal the magic' behind his work, and Grandpop was part of that.
As to his view of Chaplin's politics, Grandpop saw CC as an absolute genius as a filmmaker and performer, and more a diletante (my word, Grandpop would have said 'dabbler'

in most other areas. But he saw CC's political positions as the logical extensions of the attitudes Grandpop saw and spoke of re. Chaplin's relations with his crews (and Unions) and his overriding identification with the concerns of the underdog, regardless of the position he himself achieved.
Sorry, nothing earthshakingly insightful, just obvious and honest.