We get the two private Stennis/Geralt conversations, the first is possible just after the initial Council Meeting, the second when Stennis has been accused. I think that if you miss any one of these opportunities, some of the content "carries through" to the next conversation.
We hear that
- he thinks that monarchs only speak nicely to "lesser folk" in order to get them to do things without the monarch needing to provide anything in return.
- he won't lift a finger to save Saskia's life, and considers that she's to blame for the predicament that they're in (the impending war with Kaedwen)
- he thinks he can buy a decision in his favour.
I don't place much credence in that initial conversation with Olcan.