To create a .NET class library from the command line, you can run the script
dotnet new classlib
Do that in a clean folder, and it will create a csproj file that can then be opened in Visual Studio 2017.
However, run the script
dotnet new classlib -lang f#
in a clean folder, and the fsproj file that is subsequently create cannot be opened in Visual Studio 2017. The error message reads
The imported project "C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Sdks\FSharp.NET.Sdk\Sdk\Sdk.props" was not found. Confirm that the path in the declaration is correct, and that the file exists on disk.
I have searched for clarification of this issue, and it appears that there is work ongoing to fix it, but I wondered in the interim if there are any add-ins I can install to get this working immediately.