I don't run your software, so I don't know what options you might have.
But personally, I can make do with a 90 degree chamfer mill as a suitable alias for a corner rounding endmill. Make the body diameter of the chamfer tool same as the outside diameter of the corner rounder, and the tip diameters should also match. You can fudge the numbers a little bit either way to improve the way the actual (or particular) tool seems to align itself with your workpiece.
No, they don't simulate exactly the same, but that's what you've got an imagination for