Answers for "howto change border radius of button in flutter"

rounded raisedbutton in flutter

RaisedButton(
                onPressed: () {},
                color: Colors.amber,
                shape: RoundedRectangleBorder(
                    borderRadius: BorderRadius.circular(10)),
                child: Text("Click This"),
              )

flutter outlinedbutton border radius

OutlinedButton(
  child: Text('Woolha.com'),
  style: OutlinedButton.styleFrom(
    primary: Colors.white,
    backgroundColor: Colors.teal,
    shape: const RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(10))),
  ),
)

round border button flutter

RawMaterialButton(
  onPressed: () {},
  elevation: 2.0,
  fillColor: Colors.white,
  child: Icon(
    Icons.pause,
    size: 35.0,
  ),
  padding: EdgeInsets.all(15.0),
  shape: CircleBorder(),
)