Android Launcher Icon Rounded Corner Edge Radii

Check out Google's official Material Design guidelines for Icons about two thirds of the way down the page under the sub-heading Corners.
It indicates you should use a 2px radius on the corners. If go up a few sections, under the heading Content Area you'll see this is for a 24x24 px icon. You can scale up for other resolutions from there.

The radius of the corners should be 8.33% of the size of the icon according to Materiel guidelines.

So if the size of the icon in your project is: 1000px by 1000px, then the corner radius should be 83.3px.

However, you should probably make your document bigger than that. Maybe 2000px by 2000px, and the radius:

• 2000px * 0.0833 = 166.6px

This is just in case you need to export a version of your icon that is bigger than 1k px.