Valvert is not the main hero of the story. He is not good, not bad; he is just no one. Sometimes he is nice with other people; sometimes he insults them. That is why it is hard to say concrete what a person he was.
Also, he didn’t have a lot of lines where we can see his character or reactions. Maybe the author added him to show how many unnecessary people with their dull problems exist.
Nevertheless, it is very curious to know about him more: where was he born, who are his parents, where did the study, what problems he faced during his life? It means that even this small character is described as a person we want to know more and more.
Also, what we can easily assume is that Valvert was a piece of Count’s puzzle, as he was regarded as a possible husband for Roxane, and this scheme would give de Guiche access to Roxane. Count loved Roxane, but not because of the character, but because of her body he liked and wanted to get. And with the help of Valvert, he will easily get her.
Valvert is a character who combines lots of characteristics inside of himself. That is why we can sum up that he is a complex hero. He dies in a duel after he insults Cyrano’s nose. And we are not sad about him at all. We feel nothing to this hero, as he was no one.
Viscount de Valvert in the Essays