I really appreciated that Big Show was used to deliver a knockout punch to Cena in the first hour then Roman in the second. Clearly the director is trying to establish a theme of their duality and parallel their journeys as they move towards the story's apex (at Wrestlemania).
I think an interesting distinction between the two was made as Big Show had to first knock Roman down and slam him AFTER the match before punching him, whereas with John Cena Big Show simply pulled him out during the match and punched him. Big Show is obviously a represents for time. They almost beat you over the head with this metaphor as Big Show regularly talks about major milestones - last night talking about a first job and has once portrayed the New Years Baby (the physical embodiment of time).
I believe that the distinctions in Big Show's attacks were subtle storytelling devices, Roman is on the rise and while Big Show (time) wasn't able to prevent him from losing a match against Luke Harper, there may still be some time before Roman is ready to ascend to the top, a fact that was beaten into him. The Big Show assault on John Cena happening during the match represents time catching up with him and preventing him from being as successful as he once was, further demonstrated by using a youthful opponent like Rollins and surrounding the ring with much younger men and their representation of time - Big Show.
I think that the Roman/Cena storyline is that of two hero's journeys. One on the rise and one on the fall. There was another brilliant touch that tied this theme together in having Roman tell the story of "Roman and the Beanstalk". Jack is a common nickname for John, so Roman literally replaced John with himself in the telling of a traditional folk tale, revealing his desire to replace John Cena as the hero of WWE.
Bravo Mr. McMahon