It is always best to go to the help forum of any extension to get help. Here is what they posted about your problem. I read through the thread - good news for you!

https://community.webroot.com/t5/Webroot-SecureAnywhere-Complete/Firefox-57-and-Webroot-extensions/m-p/305838

I had already been to the help forum. I just didn't understand what I found there. I thought talking to a human would help. Imagine my dismay upon discovering that Support was non-human too. I give up. Perhaps I can squeeze the information out of Explorer. Thanks for nothing.

I posted a link to their support forum. You should ask there for instructions you can understand. There is a version of the extension that will work in 57, install it and then post in their help forum if you have problems.

As far as the add-on, Here are your choices; 1) Contact its support and ask if they will update 2) Find a replacement 3) Downgrade to a prior Firefox 4) Do without

In the event that the passwords information is lost, you should record all information in a separate text file somewhere else on your hard drive, or written down. You can easily copy and paste if you need to do so. If you are concerned about someone else looking at that file, you can compress it using a password.