TMyRadioButton = class(StdCtrls.TRadioButton)
 private
   FControlCanvas: TControlCanvas;
   procedure CNDrawItem(var Message: TWMDrawItem); message CN_DRAWITEM;
 public
   constructor Create(AOwner: TComponent);override;
   procedure CreateParams(var Params: TCreateParams); override;
end;

constructor TMyRadioButton.Create(AOwner: TComponent);
begin
 inherited;
 FControlCanvas := TControlCanvas.Create; // создаём канву для рисования
 FControlCanvas.Control := Self;
end;

procedure TMyRadioButton.CreateParams(var Params: TCreateParams);
begin
 inherited CreateParams(Params);
 with Params do // убираем стиль радиокнопки и добавляем собственную отрисовку
   Style := Style and not BS_RADIOBUTTON or BS_OWNERDRAW;
end;

procedure TMyRadioButton.CNDrawItem(var Message: TWMDrawItem);
begin // рисуем что хотим и как хотим
 FControlCanvas.Ellipse(ClientRect);
end;

TMyRadioButton = class(StdCtrls.TRadioButton)
private
  FControlCanvas: TControlCanvas;
  procedure CNDrawItem(var Message: TWMDrawItem); message CN_DRAWITEM;
protected
  procedure SetChecked(Value: Boolean); override;  
public
  constructor Create(AOwner: TComponent);override;
  destructor Destroy;override;
  procedure CreateParams(var Params: TCreateParams); override;
end;

constructor TMyRadioButton.Create(AOwner: TComponent);
begin
inherited;
FControlCanvas := TControlCanvas.Create;
FControlCanvas.Control := Self;
end;

procedure TMyRadioButton.CreateParams(var Params: TCreateParams);
begin
inherited CreateParams(Params);
with Params do
  Style := Style and not BS_RADIOBUTTON or BS_OWNERDRAW;
end;

procedure TMyRadioButton.CNDrawItem(var Message: TWMDrawItem);
var R: TRect;
begin
 R := ClientRect;
 R.Right := R.Bottom;
 FControlCanvas.Brush.Color := clWhite;
 FControlCanvas.Ellipse(R);
 InflateRect(R,-3,-3);
 FControlCanvas.Brush.Color := clRed;
 if Checked then FControlCanvas.Ellipse(R);
 FControlCanvas.Brush.Style := bsClear;
 with ClientRect do FControlCanvas.TextRect(Rect(Bottom,Top,Right,Bottom),Bottom,0,Caption);
end;

procedure TMyRadioButton.SetChecked(Value: Boolean);
begin
 inherited;
 Invalidate;
end;

destructor TMyRadioButton.Destroy;
begin
 FControlCanvas.Free;
 inherited;
end;