Can the V-22 autorotate?
The V-22 rotor disks are much lighter than a helicopter's. There's little energy available to use to cushion a landing, so although autorotation is theoretically possible, there's little point.

The Boeing V-22 handbook has this to say (see page 26):


  The V-22 is a tiltrotor and does not rely on autorotation for  a
  survivable power-out landing. The wide separation of the  engines and
  the ability to drive both rotors with one engine  make a power-out
  landing extremely unlikely. However, if  required, the V-22 can glide
  for a predictable run-on landing in  airplane mode, much like a
  turboprop


I've seen glide ratios of 2:1 and 4.5:1 quoted on the Internet, so it'll come down quite hard and destroy the rotors.

However, the design mitigates against this in various ways, or so the manufacturer claims. In the survivability section of the same handbook they say


  V-22 crashworthiness is a function of design. Heavy components,  such
  as the engines and transmissions, are located away from  the cabin and
  cockpit area. The proprotors are designed to fray or  “broomstraw”
  rather than splinter on impact with the ground. The  energy-absorbing
  landing gear system is designed to attenuate  most of the energy for
  hard landings up to 24 fps. The wing is  constructed to fail outboard
  of the wing/fuselage attachment in a  manner that absorbs kinetic
  energy and ensures the cabin area will  not be crushed, thereby
  protecting the occupants. An anti-plow  bulkhead prevents the nose
  from digging in on impact, and the  fuselage provides a reinforced
  shell that is designed to maintain 85%  of its volume during a crash.
  Aircrew and embarked troops receive  additional protection from
  crashworthy seats that stroke vertically to  absorb energy.