I had the same problem. They returned it to the GAC, in both 32-bit and 64-bit versions:
gacutil /l Microsoft.Interop.Security.AzRoles
Microsoft (R) .NET Global Assembly Cache Utility. Version 4.0.30319.1
Copyright (c) Microsoft Corporation. All rights reserved.
The Global Assembly Cache contains the following assemblies:
Microsoft.Interop.Security.AzRoles, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=AMD64
Microsoft.Interop.Security.AzRoles, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=x86
Number of items = 2
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