When you place a TsRoundBtn on a Form and bring it to the front, the surroundings of the button show the form's background, not the background of the controls that are below it.
Have a look at this picture:
[attachment=8560:acPC+RB.jpg]
The surroundings of the button show the form's background.
This is the test project: [attachment=8561:acPC+RB.zip]