So with Casey we see some looks of general coolness, like he's carefree and badass.
With Saero, we see Neutrality, but also confidence and determination
With Ruth, we see annoyance and boredom, as if she's been indifferent to the world for quite some time.
With Cameron, he has a look of support, help and happiness on his face, like he's always ready to help you out no matter how crazy whatever you're doing is. Like a sidekick. Or an RPG pedestrian. No offence.