The Oscar-winning actress played a new game with the late-night host, aptly called "Face Balls," in which Fallon and Roberts pelted giant inflatable balls at each other at point blank range.
"This is like the comedy version of '50 Shades of Grey,'" the 46-year-old actress observed during the segment.
The purpose of the game was to play footage of the impacts back in slow motion for comical effect.
"I feel bad doing it, you're America's Sweetheart, I love you," Fallon said when it was his turn.
There may have been some guilt, but that didn't stop Fallon from pelting Roberts square in the face. At one point, the audience gasped when Roberts was struck, as seen in the below video: