A 17-year-old Oxon Hill youth was sentenced yesterday to serve a minimum of 57 years in prison for his role last year in a series of rapes and robberies in which District residents were assaulted in their homes.

Rodney C. Williams of 5128 Deal Dr. had pleaded guilty to five counts in a 44-count indictment stemming from incidents last August and September. D.C. Superior Court Judge Robert A. Shuker ordered Williams to serve 15 to 45 years on each of three counts of rape while armed, 10 to 30 years for armed robbery and two to six years for sodomy.

Shuker, calling the incidents "chilling, frightening, depraved criminal conduct," ordered the sentences to run consecutively for a total of 171 years. Williams must serve one third of that sentence before he will become eligible for parole.

Williams admitted participating in four incidents in which armed men forced their way into homes, raped female occupants and stole valuables.

Williams' attorney, saying that Williams had participated in the crimes but had not instigated them, asked Shuker yesterday to impose a youth sentence, under which Williams would be eligible for parole after he acquired learning and vocational skills.

Most participants in the youth program are released after serving a few years. Assistant U.S. Attorney F. Joseph Warin asked for a maximum adult sentence, saying that Williams had willingly participated in each of the incidents.

Shuker, in imposing sentence, said Williams' chances of rehabilitation are "very, very dim . . . . The public," he said, "needs to be protected from marauders, bandits, like Mr. Williams."

"I'm very sorry that it happened," Williams told Shuker. "I wish there was some way that I could help and repay the people who were hurt."