It’s also worth pointing out that Sylvester Stallone is reportedly playing a member of the Nova Corps in the sequel.
So if Rosenbaum “sort of works in tandem” with Stallone’s character, the first idea that comes to mind is that Rosenbaum is a fellow Nova Corps officer.
In any case, if you have your own ideas about who Stallone and Rosenbaum are playing, let us know in the comments below.
Maybe it will be similar to John C. Reilly’s involvement as Rhomann Dey in the first Guardians movie.