For one, it's not simply the OS version you have to worry about. Rooting is very device specific, so you'll need to research each device you have for how to root them (I don't trust automated rooting programs). Worst case scenario is you brick the device during the root process, so make sure you do everything to a T. For example, if you have a Verizon branded phone, you are not likely able to root with the same method as an unlocked version of the same phone. Even the current security updated version of your device matters, as their updates often patch the exploits used to gain root. So don't think you can use a random Nougat based set of instructions to root and be successful.
The XDA Developers site is one of the best places to find rooting info for specific devices.