OAKDALE, LA., NOV. 28 -- Church and government sources said Auxiliary Bishop Agustin A. Roman of Miami flew today to Oakdale, where more than 1,000 Cuban inmates holding the federal detention center here had demanded that he be allowed to witness the signing of an agreement for the release of their 26 remaining hostages.

The inmates indicated early today, on a bedsheet banner displayed for television cameras, that they were waiting only for Roman before ending their eight-day-old siege. They burned buildings and took 28 hostages Nov. 21 to protest a diplomatic pact to deport about 2,500 Cubans who arrived in the 1980 Mariel boatlifts.

An agreement reached with the inmates Thursday night fell apart Friday because of what Sen. John B. Breaux (D-La.) called "add-ons" by the Cubans. The banner hoisted this morning said, "America, do not be deceived. The BOP {Bureau of Prisons} is delaying release by denying Archbishop San Roman from attesting to the agreement. Why?"

Roman, a Cuban exile, was on his way this morning to Atlanta -- where Cuban inmates holding the federal penitentiary there for a sixth day set new fires in unoccupied buildings tonight and issued their first public demands -- when his military plane was diverted to Oakdale, a Justice Department source said.

Federal officials in Atlanta said today that they had cut off water to the prison and pressed the factionalized inmates to speak with one voice in negotiations for the release of their 94 hostages. Inmates there had also requested Roman's presence.

Fr. Robert Lynch of the Miami Archdiocese said Roman, 59, had flown to Washington at 4 a.m. Thursday to meet with Attorney General Edwin Meese III. Meese declined his offer to intervene directly, Lynch said, but indicated that Roman could be a "heavy player" when the situation stabilized.

After the banner went up here today, Justice Department spokesman Mark Sheehan said, "We don't negotiate by signs." At an evening briefing, he refused to comment on Roman and said, "We have no present plan to put any third party in the negotiations." He said no talks were held today and none were scheduled Sunday.

Earlier today, authorities barred the news media from the section of the prison parking lot where the inmates' banners had been visible.

They also erected a 10-by-20 foot plywood barrier in front of the building at the center's gate where negotiations have taken place. A Justice Department spokesman said the barrier was intended to block noise from a power generator.

A spokeswoman for the Miami Archdiocese told the Associated Press today that Roman had flown to Oakdale this morning. Immigration and Naturalization Service officials here would not confirm or deny that he had arrived or was expected.

At a noon news conference in Washington, Bureau of Prisons Director J. Michael Quinlan said federal authorities had not ruled out allowing an outside mediator to participate in the talks.

According the Coalition to Support Cuban Detainees, an Atlanta-based group, Roman had talked to detention center Warden J.R. Johnson last Sunday about participating in the talks here.

Steven Donziger, a coalition spokesman, said Roman told him Tuesday that Quinlan had asked him not to travel to Oakdale then because his presence could be "disruptive."

Roman has publicly criticized the revived U.S.-Cuban agreement that eventually could result in the deportation of about 7,000 Marielitos. Speaking on a Miami radio program Nov. 20, Roman encouraged Cuban natives to register their objections.

"Everyone needs to get moving," he told listeners of WAQI. "There needs to be a letter from each family. This is the moment to respond against an injustice."

In a recent statement about Cuban detainees, issued before the uprisings, Roman said, "The indefinite imprisonment of human beings who are not serving their sentences due to crimes they have committed cannot be justified."

About half of the 2,500 Mariel refugees who could be deported immediately under the revived agreement are being detained after finishing jail or prison sentences for crimes committed in the United States. Many others received immigration parole after serving criminal sentences. Their convictions cost them their right to remain and seek permanent residence.

Meese offered a moratorium last Monday on such deportations and a case-by-case review of the inmates' immigration status in the "expectation" that the uprisings would end.

Inmates here reached an agreement Thursday to sign a typed accord Friday that would result in the hostages' release. In a videotape, inmate Manuel Monzon was seen shaking hands with a federal negotiator who said, "We have a deal."

One hostage was released then as a sign of good faith. A second was released Friday after being stabbed in the neck by an inmate who was then handed over to authorities in handcuffs by fellow prisoners. The wounded hostage was recovering.

Sen. Breaux said Friday that the agreement collapsed because the four inmate spokesmen were unable to persuade all of the inmates to support it and tried to amend it.