Rosso 2's or Diablo Rosso corsa ? The Rosso 2 is a sport touring tyre and not really comparible to the supercorsa ... Diablo Rosso Corsa is oe fit on the 899, I like them but do prefer supercorsas ultimately for grip. Don't last as long though.
I'm running supercorsa on my 899 and I've done a rear in 500 miles, the longevity of the Rosso will be more but not having run one I can't imagine the grip is as good as supercorsa. If you change let me know if the difference is that noticeable