I have a SQL Server 2008 DB with many tables filled with data and I used SQL Server Management Studio to generate a SQL dump by using the Script Wizard : Tasks -> Generate S
Try updating the web config file with correct version of System.Web.Security.SqlRoleProvider
You can find the below configuration in c:/windows/microsoft.net/framework/v4.0.30319 or any other version , there you can find config file . Into it check for machine config files to get version & public key.
For .net frameowork 4.0
for .net framework 2.0