Elizabeth Dole, according to her speechwriter Rick Smith, "has always been admired for her poise in public. This dates to her early days as a beauty contestant. Back then, she learned how to stand all day without a hair out of place--to wear a smile as permanent as the Mona Lisa's--and to respond with meaningless answers to vapid questions.

"In short, it was excellent preparation for membership on the Reagan Cabinet."

Smith was one of those turning the spit at a roast of the transportation secretary given by the Cooperative League of the USA last night. Along with tributes to her intelligence, industry and beauty, there were bright remarks, sharp retorts and even songs that raised some eyebrows. The secretary kept her smile through it all at the dinner for 250 in the Sheraton Washington Hotel Ballroom.

"People accuse the Doles of being ambitious," Smith went on to tell the audience. "I don't know why. Just because their doorbell plays 'Hail to the Chief' and Elizabeth likes to do her housework in the robes of a Supreme Court justice . . . it was a little embarrassing when she met Thurgood Marshall . . . he wanted to shake hands; she wanted to take his pulse.

"Secretary Dole," Smith said, has wanted to reach all sorts of voters but "the administration wanted to appeal to union members--but then came the recession. It wanted to appeal to women--but then came the defeat of ERA. It wanted to appeal to blacks--but then came the Bob Jones case. The way I figure it, if the administration ever decides to appeal to the Russians, we're all in big trouble."

Secretary of Agriculture John Block, who with his wife, Sue, was celebrating their 25th wedding anniversary last night, sang and accompanied himself on a guitar. His first song was the country-western tune "Lucille," about a woman who left her husband with four hungry children and a crop in the field to pick up men in bars. Block invited the audience to sing the refrain, and a smattering of people joined in.

Block's second song was one he said he wrote the words to himself to the melody of "Mamas Don't Let Your Babies Grow Up to be Cowboys."

"Senators ain't easy to love and they're harder to hold. They'd rather give you a speech than diamonds or gold--Mamas, don't let your babies grow up a-goin' to Congress, 'cause they'll never stay home, and they're always alone, even with someone they love."

Sen. Robert Dole of Kansas, the secretary's husband, said on the podium, "I'm the rest-stop speaker. There are nine more after me. There'll be more music--I hope not . . ."

After the dinner, Bob Dole, asked if he found Block's songs tasteless, said, "I listened very carefully to see what the message was, but I never did get it."

In his speech, Bob. Dole had indicated that he was willing to be "the First Man."

Secretary Dole, replying to her roasters, said: "Lyn Nofziger has told President Reagan how to settle the budget. Put July on Visa and August on Master Card."

Coop League president Morgan Williams was administrative assistant for agriculture for Sen. Dole for several years.

Other guests included: Gregory L. Karam, the Cincinnati air controller who is credited with saving many lives in the recent crash of a Canadian airplane (he was given a standing ovation); W. Graham Clayton, the model train collector who is also president of Amtrak; U.S. Coast Guard Adm. James Gracey, and former agriculture secretary Bob Bergland.

Actress Arlene Dahl, in her speech, disclosed to the crowd that she had learned how to do the southern accent she uses on "One Life to Live" from Elizabeth Dole.

Secretary Dole, who never let her smile slip, warned her roasters that they may wake up this morning to find their streets full of potholes.