You cannot root your iPhone 7
Don’t confuse between root and jailbreak. The process of gaining full access on an Android Phone also known as superuser is called “rooting”. Jailbreaking is the process of eliminating the limitations of the iPhone or Apple devices. After Jailbreaking your device will allow installing the third-party applications away from the App Store. Apple doesn’t allow to install software outside from Appstore as they may contain some malicious code to harm the device or gain access to its credentials. Furthermore, Jailbreaking is on your own risk and it will void the warranty provided by the manufacturer.
For more information – Rooting Android vs Jailbreaking iOS