No, there will not be NTR in this VN. So this is most likely just Melody getting dirt on Mr. Roberts. The relationship you're imagining between Melody and Mr. Roberts will not happen. He's just a dirty old man character.
I know the topic of NTR can be confusing on F95 because I've seen a billion and one of people's personal definitions on F95, each more ludicrous than the next. The Netorare trope is when the MC's committed lover is stolen away by an antagonist.
That will not happen in this VN. MC isn't even in a relationship with anyone to begin with.
Further more, there will not be any sexual interactions between any of the LIs and other men. There may be nudity or flashing in front of other people and there might be teasing, but that isn't even close to being in the same realm as NTR. If that still bothers certain people though, then those people are probably better off looking for a different VN that suits their sensitivities.