Details and Conditions
I have seen several posts from the developers on the Rocket League forums when Psyonix was an independent developer approving of YouTube monetization but I have never found an official policy statement. Psyonix has since been acquired by Epic Games so it is assumed that the video policy for Rocket League is the same as Epic Games' policy. Keep in mind that you should only monetize Rocket League videos if you are not listening to the soundtrack in the game as it features licenced music that could result in a copyright claim. The game also features content such as logos and other content from other companies which could also result in a copyright claim.