ROANOKE, Va. (AP) _ A former Coca-Cola bottling official who said he was ordered by superiors to help fix the price of soft drinks has agreed to testify before a federal grand jury.

Raymond H. Rissmiller, 44, pleaded guilty Monday under an agreement that calls for his cooperation with grand juries and at any trials he is called before in a price-fixing probe going on around the nation.

Rissmiller faces up to three years in prison and a fine of $250,000 for his plea to a charge of conspiring to fix the prices of products of the Coca-Cola Bottling Co. of Roanoke Inc., which was known as Wometco Coca-Cola Bottling Co. of Roanoke Inc. before being purchased in 1985 by Coca-Cola Bottling Co. Consolidated of Charlotte, N.C.

Federal charges filed against Rissmiller said he was a vice president of Wometco and later a director of sales for Coca-Cola Bottling Co. of Roanoke.

U.S. District Judge James C. Turk delayed sentencing pending the outcome of the price-fixing probe.

On Friday, a former president of a Pepsi-Cola bottling company in Maryland entered a guilty plea in a price-fixing scheme in Norfolk. James P. Sheridan, of Timonium, Md., also agreed to help prosecutors unravel allegations of price-fixing in the soft-drink industry.

The Justice Department has been conducting investigations of price-fixing in the industry in 11 areas of the nation, officials have said.

An indictment against Rissmiller said that from as early as 1982 and at least through November 1985, some soft drink bottlers conspired in western Virginia to fix the price of their products. In addition to the two companies Rissmiller worked for, the other companies were identified in court papers only as ''co-conspirator bottling companies.''

The indictment said the companies held meetings and discussions to coordinate promotional letters they sent out and also to raise the wholesale prices of 16-ounce nonreturnable drinks and other products.

The conspiracy kept the prices of colas high and prevented the operation of an open and competitive market in the industry, prosecutors said.

An attorney for Rissmiller, Charles Dorsey, said Tuesday that Rissmiller was fired by the Roanoke bottling company in April by company officials who accused him of violating corporate policy by discussing prices with competitors.

But Dorsey said in a telephone interview that Rissmiller had been acting under orders from superiors when prices were discussed with competitors over a four-year span.

A spokesman for the North Carolina parent company, Mike Bascle, said Tuesday from his Charlotte office he could confirm only that Rissmiller was a former employee in Roanoke.

Previously, Bascle had said his company has strict rules prohibiting employees from discussing prices with competitors, adding that he knew of no cases in which such punishments had been imposed.

Asked whether Rissmiller left the company under such a circumstance, Bascle said, ''I'm not in a position to know that.''

Asked whether any corporate officials had been ordered to appear before the grand jury, Bascle said, ''I'm not in a position to know that, either.''

He said he knew of no price-fixing being done by his company. Within the last year, a Pepsi bottler in Washington D.C. and a Virginia Coca-Cola official were convicted in price-fixing cases.

Rissmiller, a former pro football player, was chosen by the Philadelphia Eagles in the second round of the 1965 NFL draft. He then suffered a knee injury and was able to play as offensive tackle only during the 1966 season, a spokesman for the Eagles said Tuesday.