Richard Baker, in perhaps the best selling Zen book in the English language, Zen Mind, Beginner's Mind describes the term roshi in the following manner,
Quote:
A roshi is a person who has actualized that perfect freedom which is the potentiality for all human beings. He exists freely in the fullness of his whole being. The flow of his consciousness is not the fixed repetitive patterns of our usual self-centered consciousness, but rather arises spontaneously and naturally from the actual circumstances of the present. The results of this in terms of the quality of his life are extraordinary-buoyancy, vigor, straightforwardness, simplicity, humility, security, joyousness, uncanny perspicacity and unfathomable compassion. His whole being testifies to what it means to live in the reality of the present. Without anything said or done, just the impact of meeting a personality so developed can be enough to change another's whole way of life. But in the end it is not the extraordinariness of the teacher that perplexes, intrigues, and deepens the student, it is the teacher's utter ordinariness.
It should be noted that this was written as the introduction to the words and teachings of Mr. Baker's teacher, Suzuki- roshi. This introduction was meant to describe a real person, and by extension, as is clearly stated, all people with the title roshi. It is not an idealized reference to a heavenly being or some distant or mythological religious figure.
Zen Master Seung Sahn, who is the most famous Korean Zen Master in the West, in Dropping Ashes on the Buddha , one of his better selling books, related the following exchange of letters that indicates his view of the Zen Master. In a letter to the Master, someone asked, "If a Zen Master is capable of doing miracles, why doesn't he do them?... Why doesn't Soen Sunim do as Jesus did- make the blind see, or touch a crazy person and make him sane? Wouldn't even such a showy miracle as walking on water make people believe in Zen so that they would begin to practice..." The Master (that is, Seung Sahn) replied, "Many people want miracles, and if they witness miracles they become attached to them. But miracles are only a technique. They are not the true way. If a Zen Master used miracles often, people would become very attached to this technique of his, and they wouldn't learn the true way..."
...
The well known Chinese Ch'an teacher, Master Sheng-yen also said of the Zen Master, "it should be remembered that the mind of the master is ever pure... and even if the master tells lies, steals, and chases women..., he is still to be considered a true master as long as he scolds his disciples for their transgressions."
http://terebess.hu/english/lachs.html