OTA update

As we get closer to 6.0 update. I'm new to the rooting scene. I recently rooted my nexus 6 and was wondering where I could find the download for all the Google OS updates, I've heard you cannot download Ota anymore unless you reflash the system.img

Also. Once I download an updated img, how do I apply it?

Sent from my Nexus 6 using XDA Free mobile app