Lachs, in the former link, quotes Richard Baker quoting Trudy Dixon:
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.
Lachs goes on:
Most students will understand the term Dharma transmission as a sort of USDA seal of approval guaranteeing that the Master/roshi is fully enlightened, and that his or her every gesture therefore manifests the Absolute. This attitude is well illustrated by one of the responses to my questionnaire: "a Zen Master is a person who has been certifiedas existing in fully awakened mind..."
Now I will give Lachs no argument at all that Baker has written an example of bullshit. As Harry Frankfurt wrote:
To begin with, whenever a person deliberately misrepresents anything, he must inevitably misrepresenting his own state of mind. It is possible, of course, for a person to misrepresent that alone — for instance, by pretending to have a desire or a feeling which he does not actually have. But suppose that a person, whether by telling a lie or in another way, misrepresents something else. Then he necessarily misrepresents at least two things. He misrepresents whatever he is talking about — i.e., the state of affairs that is the topic or referent of his discourse — and in doing this he cannot avoid misrepresenting his own mind as well. Thus, someone who lies about how much money he has in his pocket both gives an account of the amount of money in his pocket and conveys that he believes this account. If the lie works, then its victim is twice deceived, having one false belief about what is in the liar’s pocket and another false belief about what is in the liar’s mind.
So while I largely agree with Lachs, I have to mention something that came as a shock to me last night. My Japanese dictionary defines roshi as:
老師 【ろうし】(n) old priest, sage, (Zen) teacher
Last night I had to take my son to his Chinese class. Guess what the Chinese word for teacher is? It's lao shi- with the latter character slightly simplified. That is, in Chinese, an everyday teacher is a "roshi."
In Japanese, by contrast, of course the word used is sensei ( 先生【せんせい】); and I am but a lowly Ph.D. (博 【はく】).
So, basically the Japanese term for a Zen master most often used is, rendered in English, "teacher," which, in that field, anybody can indeed give themselves or be bestowed upon them as an honorific title. But it means exactly whatever is behind it; which is either a lot or a little.
And that's your Chinese/Japanese/Buddhist caveat emptor lesson for today.