My Google-fu has failed: I can only find downloads compatible with Visual Studio 2012.
I remember it being available for 2010 originally:
Introducing the Microsoft “Roslyn” CTP – The Visual Studio Blog – Site Home – MSDN Blogs
Is the Roslyn CTP still available for VS2010 SP1?
The latest version doesn’t support Visual Studio 2010, now that Visual Studio 2012 has launched:
The older binaries are still available on NuGet (scroll all the way down to Version History) which should still be compatible with VS2010, but as mentioned those are older builds. Gotta move along with the times, they say…