Republican Senate candidate John W. Warner risked ruffling hometown feelings in this western Virginia city yesterday to prove his loyalty to conservatism and to the principle of non-intervention in labor disputes.

At a press conference after this third televised debate with his Democratic opponent Andres P. Miller, Warner told reporters that in 1970 he voted for the reelection of Virginia's conservative Independent Sen. Harry F. Byrd, Jr. instead of Republican nominee Ray Garland, a popular state legislator from Roanoke and a leader of moderate Virginia Republicans.

Warner also said in the debate and news conference that he opposes industrial mutual aid agreements such as the one among railroads that recently provided the Norfolk and Western Railway, headquartered in Roanoke, with $800,000 in aid during an 80 day strike.

Warner's revelation that he deserted his party's nominee to vote for Byrd came in connection with his accusation that Miller should be labeled a liberal for supporting such Liberal Democratic candidates as Henry E. Howell, who ran for governor last year, and George C. Rawlings, Byrd's Democratic opponent in 1970.

Warner said he put "principle above party" to vote for Byrd in 1970. Miller said he had always abided by his party pledge to support Democratic candidates, but tried to discourage Byrd's 1976 foe, retired Navy admiral Elmo R. Zumwalt, from running.

Miller calls himself a "moderate-conservative" and has been an intraparty foe of both Howell and Rawlings. Miller again excluded himself from his party's liberal wing yesterday by saying. "I do not come from the same wing as say, Mr. Howell."

Howell, the populist champion of black Virginians, labor and consumer advocates, beat Miller in last year's party primary for governor, and has pledged his support for him in this Senate contest. Some of Howell's strongest supporters who have been working for Miller, especially in Northern Virginia are upset that Howell is being excluded from any formal role in Miller's campaign.

Warner continues to try to link Miller and Howell in speeches and campaign literature. He suggested in Richmond Tuesday that Miller would support a nomination by President Carter of Howell to the U.S. Court of Appeals.

Warner said he would vote against confirmation of Howell should he be nominated by Carter for a judgeship. Miller said in his press conference after the debate that he would seek the advice of the judicial nominating commission on all judgeships and "would not oppose any nomine submited by the president who was approved by the commission."

The question on mutual aid pacts among companies dealing with the same labor unions came up in connection with a food stamp issue that divides the candidates. Warner again said in answer to a question that he opposes distribution of food stamps to strikers during labor disputes. Miller said he would deny them to strikers but not to their families.

Warner added; " . . . but by the same token I do not approve of these mutual aid pacts by which industries aid companies involved in labor disputes." Miller says he sees nothing wrong with such pacts "so long as federal funds are not involved."

In answer to several questions, Warner criticized Miller's proposal to create three cabinet-level appointments to fill the functions of the Department of Health, Education and Welfare.

"This is the issure where a Grand Canyon separates my opponent from me," Warner said. "He talks one day of limiting government and the next about taking the biggest and most wasteful federal agency and dividing it into three new agencies . . . There never has been a federal agency created that did not grow and grow and grow . . ."

Warner said in his press conference that he believes he is winning the television debates on the HEW issure and on his advocacy of one-third across-the-board tax cut over three years.

Miller defended his HEW plas "as a means of taking this mommoth, agency and breaking it up into manageable parts." He said he believes he is winning the debates primarily on the tax issue by insisting that any tax reduction be offset by dollar-for-dollar cuts in spending to prevent increases in the federal deficit.

The Roanoke debate and the one last week in Norfolk were sterile affairs with the candidates answering questions by a panel of reporters and given no opportunity to challenge one another directly. By contrast, their first debate in Washington several weeks ago included several sharp exchanges.