Create New Role Manually Using EF?

Using the Entity Framework that I generated. I have a Roles table created during the default system AspNetSqlRoleProvider security set-up.In the Roles table, I have an ApplicationId uniqueidentifier column. Which has a guid populated in it, which doesn't change for my application. I need to add a Role manually through my app using the entity framework. However, when creating my Roles object and setting Roles.ApplicationId. It expects a type of Guid. I have the ApplicationId in my web.config app settings. As it shouldn't change. But it is returned at string. I cannot type cast the value either to use in Roles.ApplicationId. What can I do to use my current ApplicationId value when trying to create a new role manually using the EF?