This script allows you to expand Rocket League's horizontal resolution to fit up to 2 monitors. It opens a cmd window, prompts you for an integer value(1 or 2), then it starts Rocket League to fit 1 or 2 monitors.
Changes the string 'ResX=1920' in %MyDocuments_Location%\My Games\Rocket League\TAGame\Config\TASystemSettings.ini to 'ResX=3840'.
Download dist directory.
Edit values in dist\config.txt
Execute rocketResX.exe