I've had two 2012 wrx's (its a long story)both hatches and both have had the OEM snowboard and ski rack. On the first, I was a noob to racks and decided not to buy the lift kit. I live about 15 minutes from the nearest ski slope so I go all the time, and unfortunately I paid the price for not buying the risers. Within the first couple visits, I noticed a small pressed in dent in the center of my roof, directly under where the bindings sit. My advice to you: spend the $16 (or whatever the cost is) and buy the risers. Unfortunately if you're a snowboarder like I am, most bindings will still gently rub against your roof on the lowered side of the rack. Simple fix: A. put the girlfriends snowboard on that side
or B. Take a rag or t-shirt and just tie it around the binding straps to prevent rubbing.
Whatever you decide, just remember its cheaper to buy the risers and hate the look then it is to pop a roof dent...(and still hate the look)
Sorry for the crappy cell phone pics