An example straight out of Borland's official FAQ:

procedure TForm1.Button1Click(Sender: TObject);
var
  lf : TLogFont;
  tf : TFont;
begin
  with Form1.Canvas do
    begin
    Font.Name := 'Arial';
    Font.Size := 24;
    tf := TFont.Create;
    tf.Assign(Font);
    GetObject(tf.Handle, sizeof(lf), @lf);
    lf.lfEscapement := 900;
    lf.lfOrientation := 900;
    tf.Handle := CreateFontIndirect(lf);
    Font.Assign(tf);
    tf.Free;
    TextOut(20, Height div 2, 'Rotated Text!');
    end;
end;