The D.C. Bar's disciplinary board has asked the city's highest court to suspend former Superior Court Judge Harry T. Alexander from practicing law for three months because he allegedly neglected to represent his clients in two criminal cases.

In one case, according to a report made public yesterday by the Board of Professional Responsibility, Alexander failed to appear in court in August 1980 to represent a man in a probation revocation hearing. The man's probation was revoked and he spent six months in prison.

The board, upholding a decision reached by a three-member disciplinary committee last September, concluded that Alexander "showed a callous disregard of his client's interests . . . and a failure even to concern himself with the client's six months' incarceration -- all because Alexander was still owed $500 on his $2,000 fee."

Alexander, who resigned from the court in 1976 and entered private law practice, yesterday declined to comment on the board's action, saying only that he definitely would appeal the decision to the D.C. Court of Appeals, which makes the final determination on disciplinary matters.

The board's report said Alexander had been warned about neglecting clients on three prior occasions in the last 2 1/2 years, showing a pattern of "repeated neglect . . . and at times a callous disregard for the interests of his clients."

In a separate report, the board also recommended a 90-day suspension for well-known defense lawyer Sol Z. Rosen. The board, upholding the findings last fall of two disciplinary committees, said Rosen neglected the 1980 case of a man accused of petty larceny and that Rosen's "failure to act on his client's behalf contributed to" the man's spending two months in jail.

In another case, Rosen, who could not be reached for comment yesterday, was accused of revealing a confidence, or secret, of a client without that client's consent.