Revzilla describes the Rosso 3 as a "superbike" tire, suitable for large, powerful sportbikes. The rear tire is offered in sizes up to 190. I do not think this is a very appropriate replacement rear tire for the 390, because it does not come in the size that actually fits the rim: 140/70/17. The stock 150/60/17 is too wide and must be squeezed onto the rim, resulting in profile distortion that does not allow the tire to put its full designed contact patch on the road. The 140 fits and puts down a bigger contact patch, with no chicken strips. There are an increasing number of 140/70/17 tires on the market now, as all the Japanese manufacturers now have entries in the growing <400cc class. All the Japanese bikes use a 140/70/17 rear tire, on the same size rim as the KTM 390. Michelin, for example, has recently marketed a variant of its Pilot series targeted at the <400 class: the Pilot Street Radial.
Tweak, I also follow the RC Forum, where there is constant discussion of tires and performance issues. Many of the RC racers have converted to 140/70 rear tires with great success, and there is a growing consensus that 140/70 is the proper size for the 390's rear rim.
I have been running a Bridgestone EVO S20, 140/70 on my Duke for several months, and I have to say that I am more than delighted with it. It somehow feels more stable and natural on the bike than the (oversized) 150/60 OEM Rosso II. The dry grip is outstanding, and the S20 gives a more comfortable ride than the Rosso II. No chicken strips! The contact patch goes right to the edge. The S20 is a soft sport tire like the Rosso II, and appears to be wearing at about the same rate, so I would expect around 4000 miles of useful life on the very abrasive road surfaces in my area. I think I might try a set of those Michelin Pilot Streets when the time comes for another tire change. Clearly, 140/70 is the sweet spot for the 390's rear tire and I now would not consider using any other size. One small additional benefit is that the 140/70 is slightly taller than the OEM 150/60, so that gives you a bit of additional ground clearance and makes scraping your pegs less likely on turns.
I am still running my OEM Rosso II on the front, Tweak. It is holding up well at 5.8K miles, and is a fine tire. It has plenty of miles remaining. I expect it will be time to fit a new front tire when the current rear tire is ready to be changed. I run tires front and back at around 28-29 lbs.
My bike is going in next week to refit my ABS , valve check and change rear and front tires . I have decided upon the Michelin Road III . They should give me a little more grip in the wet than the stock Rosso 2 .