We're having frequent roaming and disconnect issues with Apple products, so far Ruckus support hasn't been very helpful or insightful. I've recently tested ofdm-only, but it doesn't seem to be a silver bullet.
I've got R710s almost at min tx power due to the density of our deployment and limitations of the building's design (i.e. one main floor with Mezzanine levels above some areas...cinderblock walls, concrete floors, etc.)
Ok, look at this from a different angle; roaming is a client orientated function so maybe you need to look at the WLAN properties so see if they are 'optimized' for Apple devices. Apple devices are very specific about how they work but on the plus side its normally well documented. take a read of this and I would suggest making use of 802.11r