What is Ray Bradbury's tone about the rocket men?
Tone, of course, is an author's attitude towards his or her subject. I am intrigued by your question because more than one of the stories within The Illustrated Man collection by Ray Bradbury concerns the "rocket men" you mention in your question. In reality, though, that doesn't matter because Ray Bradbury's tone toward any of "the rocket men" you ask about is always the same: it is a tone of both disillusionment and disagreement.
There are three stories in question all of which contain the aforementioned "rocket men": "The Rocket," "The Rocket Man," and "Kaleidoscope." In the former story, a guy wastes his savings in order to simply pretend or "simulate" a real rocket trip because he can't pay for a real one. The author, Ray Bradbury, reveals his tone indirectly through the happenings of the story. In "The Rocket Man" a husband leaves his wife and family time and time again in order to go back to the alluring "drug" of the stars. Humanity is left behind for the romantic ideal of starlit space. Again, Bradbury shows his own thoughts indirectly by showing that no good comes from this husband's space travel. The latter story, "Kaleidoscope," all of the "rocket men" here are thrown tragically into space (to certain death) when their spaceship explodes. Here, Bradbury reveals his thoughts in the character of Hollis who realizes that the illusion of dreams can't constitute a memory of reality. One of the best quotes that sums up the tone is about the mother in one of the stories who is steeped in reality (as opposed to the "dreams" of the "rocket men"):
Mother wasn't afraid of the sky in the day so much, but it was the night stars that she wanted to turn off, and sometimes I could almost see her reaching for a switch in her mind, but never finding it.
In conclusion, it's important to note that no matter which story you are referring to, Bradbury's tone remains the same: one of disagreement or disillusionment towards the "rocket men" and their space travel. This leads to a further idea that the simpler the life is, the better for the human race.