A Prince George's County man was found guilty of armed robbery and burglary yesterday in a trial that was postponed for several months after the man's estranged wife, who was to be a prosecution witness, and three other persons were found slain on the day of the scheduled trial.

Ronald Resper, 30, of 2234 Alice Ave., Oxon Hill, was convicted by a D.C. Superior Court jury of the 1982 armed robbery of a Northwest Washington towing company where he had worked periodically. Resper's brother Wayne, who also was charged with armed robbery of the firm, was acquitted yesterday by the same jury.

No arrests have been made in the April 9 slaying of Resper's wife Carolyn, another woman and two men who were found shot to death in the Southeast Washington apartment Carolyn Resper shared with the other slain woman. The quadruple slaying was the largest multiple homicide in the city in more than a dozen years.

Before the start of the trial this week, Judge Nan Huhn cautioned lawyers and witnesses to refrain from mentioning Carolyn Resper's death during testimony. After the verdict, Ronald Resper was held without bond.

Resper could face maximum life sentences for the convictions on charges of armed robbery and second-degree burglary while armed. He also was convicted of destruction of property and unauthorized use of a motor vehicle.