The instructions on http://www.telerik.com/blogs/fiddler-for-linux-beta-is-here for installing Fiddler for Linux Beta mention running /usr/lib/mono//mozroots --import --sync. However I don't have that application. Instead, mozroot is to be found in /usr/lib/mono/4.5. The documentation might confuse some folk.
For info, Linux Mint 18.1. Mono installed through apt install mono-complete.
Just a quick aside, why does the forum sign-up insist on the user entering a company name? We don't all work for companies.