public partial class Role
    {
        public Role()
        {
            User = new HashSet<User>();
        }

        public int RoleId { get; set; }
        public string RoleName { get; set; }

        public ICollection<User> User { get; set; }
    }

public partial class User
    {
        public int UserId { get; set; }
        public string Login { get; set; }
        public string Pass { get; set; }
        public int? RoleId { get; set; }

        public Role Role { get; set; }
    }

modelBuilder.Entity<Role>(entity =>
            {
                entity.Property(e => e.RoleName)
                    .IsRequired()
                    .HasMaxLength(32)
                    .IsUnicode(false);
            });

            modelBuilder.Entity<User>(entity =>
            {
                entity.Property(e => e.Login)
                    .IsRequired()
                    .HasMaxLength(32)
                    .IsUnicode(false);

                entity.Property(e => e.Pass)
                    .IsRequired()
                    .HasMaxLength(32)
                    .IsUnicode(false);

                entity.HasOne(d => d.Role)
                    .WithMany(p => p.User)
                    .HasForeignKey(d => d.RoleId)
                    .HasConstraintName("FK__Users__RoleId__2B3F6F97");
            });