There is a thread on the Webroot forums about this, and here's an official answer from December 2015:
I just got off the phone with one of our team members that handles this and apparently torproject.org is classified as a 10 in our system as opposed to an 81 which is what I saw. The reason for this is because it is considered a proxy, and many large employers would not like employees navigating to this site.
There is quite a bit of back and forth on our end in regards to this and it may change in the future(hopefully) Smiley Wink
In regards to Tor itself, that is a safe website to navigate to and if you want to continue to it, when the block comes up simply click "Tell me more about it" and then click "Unblock page and continue." This should create an override on your machine and while the search results will still show the red annotations, the site should no longer get blocked upon navigation.
I will update this thread once I know more or if we make a change to this.
Online Retention Specialist