In "Cathedral", is the single primary character round or flat? And is he static or dynamic? And the secondary?

The first primary character is the narrator, who is unnamed.  The second is Robert, the blind man. 

The narrator is a round character who is also dynamic.  See the sources below for descriptions of these character types in detail.  The narrator is round because he has many aspects to his personality.  He is dynamic because he changes throughout the story.  The narrator becomes more open-minded and is able to broaden his perspective.  More importantly, this broadening understanding speaks directly to the unhappiness that he has experienced in his life.  The quotes that best demonstrate the narrator's change are:  "'fingers rode my fingers as my hand went over the paper. It was like nothing else in my life up to now.'' and "I was in my house. I knew that. But I didn't feel like I was inside anything." 

Robert is also a round character.  He is witty and funny, with a positive outlook but also realistic expectations of the world.  However, in this story, he is static.  He is the mentor that will bring the narrator to a new plane of existence, and therefore, does not and will not change as a result of the story's actions.