Simplest solution to the Roman Reigns hit and run mystery:
Heyman ran over Roman.
Roman finds out.
Heyman admits doing so. Brock supports Heyman for doing so and is glad that Heyman did it.
We get another round of Roman Vs Brock with the added angle of Brock/Heyman as the bad guys due to them literally trying to kill Roman to get people to cheer Roman. Also, Heyman gets his balls back and does his first proper act of villainy since the Dangerous Alliance saga.
Oh! Oh! Then he can also be a heel GM and we can go back to that as well!