You can try following with the values of your choice. It will make the bottom two corners rounded.
rounded_rectangle.xml
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item>
<shape>
<gradient android:angle="270" android:endColor="#404040" android:startColor="#404040" />
<stroke android:width="1dp" android:color="#808080" />
<corners android:bottomLeftRadius="11dp" android:bottomRightRadius="11dp"/>
</shape>
</item>
</selector>
then use it as a background to your listitem as follows
android:background="@drawable/rounded_rectangle"