No, root is not meant to brick your box. Read the 1st two posts in this thread how to root your box, if you really need it. I guess you want root to apply those TCP buffer settings you mentioned in your separate thread. Like Higgs mentioned, upgrade your box 1st (via FOTA app, or USB zip or flash full image), then you can root it. Theoretically yes, once rooted you may not be able to upgrade via FOTA. But you can simply unroot, using same steps as for rooting (you just need the unroot file from post #2 in this thread), do the upgrade and then root again.