Rogers is an odd bird. Sometimes he seems to believe every word that Rojack says, but other times, he seems to be convinced that it's all a lie.
As the novel goes on, however, we start to notice some key similarities between Rojack and Rogers—even their last names are similar. More importantly, though, like practically every other character in the novel, Rogers is repressing some essential truth about himself that's tearing him up inside.
Rojack and Roberts seem oddly close from the moment they meet. As they drive back to his apartment, Rojack describes feeling "the physical communion one usually receives from a woman" (3.70) with Roberts. How bizarre. Although Rojack hates pretty much every cop he interacts with, he has a clear (and rather strange) affection for Rogers.
In our eyes, this is because they're going through similar things. Rojack gets plastered all day, every day; Roberts shows up to the police station with a massive hangover. Rojack attacks and kills his wife; Roberts "had beaten" his wife and "did not even know why" (8.416). However, it's not until Roberts explains that "frustration […] is how [cops] lose it" (8.416) that we fully understand their similarities. Like Rojack, Roberts is deeply unsatisfied with his life, unleashing his frustration in some ugly ways. Even the law man, then, is irrational.