Roles.GetRolesForUser throws exception Object reference not set to an instance of an object
NOTE: according to the OP's comment himself, this answer solved his problem.
This is a .NET Framework bug.
To solve this issue call:
string[] roles = Roles.Provider.GetRolesForUser(userName);here is a very similar question.
In MVC 5 you can get user roles with GetRoles(Id) method.
But, before use GetRoles you have to make userManager object:
var userManager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(context));var d = userManager.GetRoles(5);