Multitier architecture and Identity. Why to use UserManager and RoleManager?

Microsoft Identity introduces UserManager<T> and RoleManager<T> classes to interact with AspNetUsers, AspNetRoles and the other database tables. But why we should use them? Maybe it is a better solution to scaffold the database and work with its tables directly using the Entity Framework and forget about classes UserManager<T> and RoleManager<T>?

Why am I asking?

I my application I want to follow the multitier architecture. I started with creating the DTO-class for the user:

public class UserDto
{
    public string Id { get; set; }
    public string UserName { get; set; }
    ...
    public List<RoleDto> Roles { get; set; }
}
public class RoleDto
{
    public string Id { get; set; }
    public string Name { get; set; }
    ...
}

Type IdentityUser I want to map into UserDto, type IdentityRole - into RoleDto.
As you can see, in UserDto I want to store roles of a user.
Now let's have a look at the IdentityUser type: link. It contains a lot of properties, but it doesn't have roles of the user.
So, when mapping IdentityUser into the UserDto, I need to work with RoleManager<T> to get roles of the user. I think, it's a dirty solution.

My idea

We can forget about UserManager<T> and RoleManager<T> types. We can simply scaffold the database and work with it using the Entity Framework.
After scaffolding of database I have the following:

public partial class AspNetUser
{
    public string Id { get; set; }
    public string UserName { get; set; }
    public string NormalizedUserName { get; set; }
    public string Email { get; set; }
    public string NormalizedEmail { get; set; }
    public bool EmailConfirmed { get; set; }
    public string PasswordHash { get; set; }
    public string SecurityStamp { get; set; }
    public string ConcurrencyStamp { get; set; }
    public string PhoneNumber { get; set; }
    public bool PhoneNumberConfirmed { get; set; }
    public bool TwoFactorEnabled { get; set; }
    public DateTimeOffset? LockoutEnd { get; set; }
    public bool LockoutEnabled { get; set; }
    public int AccessFailedCount { get; set; }

    public virtual ICollection<AspNetUserClaim> AspNetUserClaims { get; set; }
    public virtual ICollection<AspNetUserLogin> AspNetUserLogins { get; set; }
    public virtual ICollection<AspNetUserRole> AspNetUserRoles { get; set; }
    public virtual ICollection<AspNetUserToken> AspNetUserTokens { get; set; }
}
// AspNetUserClaim, AspNetUserLogin, AspNetUserRole and AspNetUserToken

I introduced only AspNetUser class to be short. As you can see, it has a property AspNetUserRoles - roles of the user. It's great, because now it's really simple to map this class into the UserDto.

Question

Is it a good idea to scaffold the database and don't work with UserManager and RoleManager classes? Maybe you can introduce a better solution?