Tty this if you also want to have a full-width button with icon and text:
Padding( padding: EdgeInsets.all(15), child: TextButton( child: Row( mainAxisAlignment: MainAxisAlignment.center, children: [ Text('Some Text', style: TextStyle( color: Colors.blue, fontSize: 22, fontWeight: FontWeight.w700)), Icon(Icons.arrow_forward), ], ), style: TextButton.styleFrom( minimumSize: const Size.fromHeight(50), iconColor: Colors.blue, foregroundColor: Colors.blue, side: BorderSide(color: Colors.blue, width: 2), shape: const RoundedRectangleBorder( borderRadius: BorderRadius.all(Radius.circular(12))), ), onPressed: () {}, ), ),

You can use the below code to make a rounded button with a gradient color.
Container( width: 130.0, height: 43.0, decoration: BoxDecoration( borderRadius: BorderRadius.circular(30.0), gradient: LinearGradient( // Where the linear gradient begins and ends begin: Alignment.topRight, end: Alignment.bottomLeft, // Add one stop for each color. Stops should increase from 0 to 1 stops: [0.1, 0.9], colors: [ // Colors are easy thanks to Flutter's Colors class. Color(0xff1d83ab), Color(0xff0cbab8), ], ), ), child: FlatButton( child: Text( 'Sign In', style: TextStyle( fontSize: 16.0, fontFamily: 'Righteous', fontWeight: FontWeight.w600, ), ), textColor: Colors.white, color: Colors.transparent, shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(30.0)), onPressed: () {
}, ), );