Trailing 37-36 with 14:07 left to play, Robert Morris scored 13 unanswered points, capped by McFadden's layup to go ahead 49-37 with 9:04 remaining.
Shane Gibson's layup with 1:27 left cut Robert Morris' lead to three, 62-59, but the Colonials made four free throws in the final minute while the Pioneers converted just one field goal to seal the victory.
Robert Morris shot just 34.6 percent (9 of 26) in the second half but made 18 free throws in the period compared to Sacred Heart's 11.
Gibson led the Pioneers (5-11, 3-2) with 27 points and six rebounds.
Duke and Cincinnati, 2016 NCAA Tournament teams, highlight the eight-team field for the Naismith Memorial Basketball Hall of Fame Tip-Off Tournament.
NCAA champion Villanova will play Notre Dame and Pittsburgh will play Penn State in the inaugural Never Forget Tribute Classic at Prudential Center on Dec. 10.
Florida guard Brandone Francis-Ramirez has decided to leave the team after two seasons.