Three suburban Maryland men pleaded guilty in D.C. Superior Court yesterday to rape and armed robbery in connection with a series of assaults last fall.

Rodney C. Williams, 17, and Raymond R. McLamore, 19, both of Oxon Hill, and Darryl C. Plater, 21, of Temple Hills, each pleaded guilty to three counts of rape while armed and charges of sodomy and armed robbery. McLamore also pleaded guilty to a count of taking indecent liberties with a minor child--a 9-year-old girl.

A fourth man, Thomas Smith, 18, of Oxon Hill, pleaded guilty to armed robbery. The four men, who face maximum sentences of life in prison, entered their pleas before Judge Robert A. Shuker.

Assistant U.S. attorney Joseph F. Warin said in court that if the case against the four men were tried, the government would present evidence that between Aug. 17 and Sept. 8, the group broke into four Washington homes, repeatedly raped and sodomized women who lived there and stole their valuables.

A fifth man, Terrence R. Hansford, 18, a former star wrestler at Oxon Hill Senior High School, pleaded guilty last month to first-degree burglary in connection with one of the incidents.