You just have to upgrade your Boost plan to one of their newer versions. There's no price difference or anything, so it's kinda stupid that they make you jump through that hoop, but it's simple enough to do. Once on their new plan, your built-in Hotspot will work without any rooting required. You may have to wait til your next billing cycle for the change to take effect, like I did, but hassle-free Hotspot is worth the minimal effort and wait.