I agree with Robzombie; but it should be mentioned that Michael got a drink regardless.
There is a slight chance that something more might have happened, because Michael was fond of Riley's laughter; and he seems to connect very well with the reasoning and calming Riley is capable of deploying. But is this really enough for something "slippery" happening?
Nah, I don't think so. The whole "We're Alive" show stays away from things like this. The only episode that seemed to "break this rule" was "randr", chapter 11, in which Kelly seemed to have wanted more from Kalani, Bill tried to connect with Pegs, and Lizzy and Saul had their share. But else? Yes, wait: Datu got kissed by Samanta. But that is all there is to this general topic on this audio-drama.
As for Riley's interests: I think it could be both, but mainly is about men; it is only Saul who assumes she might be a "wo-man, if you know what I mean"; but this is not supported one bit during the whole show; ever since Riley seemed to be kind of interested in Angel, and Angel is supposed to be a guy, right?

Anyway ... Since WA stays away from certain topics, there is a lot room for speculations ...

Best wishes!
Liam