Create a xml file in drawable folder like below
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle" android:padding="10dp">
<!-- you can use any color you want I used here gray color-->
<solid android:color="#ABABAB"/>
<corners android:radius="10dp"/>
</shape>
Apply this as background to button you want make corners round.
Or you can use separate radius for every corner like below
android:bottomRightRadius="10dp"
android:bottomLeftRadius="10dp"
android:topLeftRadius="10dp"
android:topRightRadius="10dp"