Character motivations are really interesting to me and this page pretty much sums up Roka. If he reports Sky, he’s basically admitting to himself that she was part of the cargo, and that’s not really something he’d like to know. If he doesn’t report her, he’s trying to convince himself that she wasn’t the cargo, obviously a much more palatable option for him. But professionally, he knows. And he’s too smart to really be able to successfully delude himself. But he’s trying.