Eric Mosley chipped in 16 points and Conger added a game-high nine boards to help St. Bonaventure (13-13, 6-7 Atlantic 10 Conference) outrebound Duquesne 35-26.
After two free throws by Conger put the Bonnies ahead 75-68 with 32 seconds remaining, Jeremiah Jones connected on a 3-pointer with 28 seconds left to cut the lead to 75-71. But that was the last basket for the Dukes as they missed their final two attempts with less than 30 seconds to play.
Conger and Johnson combined to score 13 of the Bonnies' final 14 points.
St. Bonaventure shot 54 percent (27 of 50), compared to Duquesne's 39.3 percent (22 of 56).
Quevyn Winters had 18 points and seven rebounds for the Dukes (8-19, 1-12), who have lost three in a row.
Seton Hall sophomore Isaiah Whitehead will stay in the NBA draft and not return for his junior season.
Washington State's trio of Josh Hawkinson, Conor Clifford and Ike Iroegbu have withdrawn from the NBA draft and will play their senior season with the Cougars.
Gonzaga center Przemek Karnowski, who missed most of last season with a back injury, says he is returning for another year.