I know it's old but might help anyone else.
This error occurs due to a conflict in the default project for Windows Azure Cloud Service when the web project is created with the name WebRole (Which puts the project in the same namespace as the Microsoft.WindowsAzure.ServiceRuntime dll).
To fix there are two easy options:
replace this code
@model WebRole.Models.RegisterViewModel
and add the using statement and your model without the namesapce
@using WebRole.Models
@model RegisterViewModel
Or instead one can add a namespace in the web.config inside the views folder (not the one in the root)
<pages pageBaseType="System.Web.Mvc.WebViewPage">
<namespaces>
-----
<add namespace="WebRole.Models" />
</namespaces>
</pages>
And on your views just replace the existing code with
@model RegisterViewModel
Hope it helps.