So, LineageOS has been out for a few days now. As promised, .zip packages for rooting the ROM have been put up on the community project's site, as it is not pre-rooted when flashed.
Interestingly, this uses Superuser rather than SuperSU to achieve root. Either way, root is achieved through flashing this package once the main ROM has been flashed. It also needs to only be flashed once; subsequent updates will keep root privileges. There are different packages depending on whether the device is 64-bit or not, and also packages to remove root if you so wish.
Of course, this is only the official (and recommended) root package. SuperSU can still be flashed and used - it's totally up to you - but keep in mind that it's not recommended. There are a ton of tutorials out on the web to guide you through that process, but the official approach definitely seems easier. Grab the downloads at the extras page of the LineageOS site, linked in the source.