I have a silverlight based application consisting of charts using silverlight toolkit and connected to database using RIA Services (Domain Service class, ADO.NET entity model).
Since you're using RIA Services it's possible that these assemblies are not available on your Web Role. To view all assemblies available on Web Roles, follow this link: http://gacviewer.cloudapp.net/
You should double check with the assemblies in your ASP.NET Web Role (the one hosting the RIA Services application), and change all assemblies that you cant find on the gacviewer website to CopyLocal = true
Besides that, if you activate Remote Desktop on your Web Role, you can (for testing purposes) connect through RDP and take a look at the event viewer to see what assemblies are missing.