All you need to do is
Make sure your cloud server PHP version meets your required version.
Lots of functions get depreciated in newer versions and if you upload your codebase without this check, your application may break in several places. You will be wasting lots of time in debugging your breaking code and fixing.
At times as you build new features you may be using extensions. Many times you tend to forget installation of these extensions on your server. Rollout checks all your required extensions are already installed or not. If it is not installed, it will halt the installation.
This prevents code getting broken due to a missing extension on the cloud. Hence it saves a lot of your time to find the reason for broken code and install the missing extensions.
Just commit your composer.json, composer.lock on alongside in your project. Rollout automatically installs all the required libraries via composer
There could be syntax errors in your code even after lots of quality assurance checks. Roll-out does a complete syntax check on all your php files and make sure nothing breaks after your code is uploaded to the live servers.