the inno roof rack will fit the 2012 impreza wrx, if you have the built in c-track rails on your roof like the wrx does, then you can buy the inno set up. they bolt directly onto the roof. check out ors racks direct, they have a fitment guide for all the major brands. check them out, u can find a rack for it.
the inno-sr racks will attach to th einside of the door jam. check them out. i just installed mine, will post pics for u tomorrow if you're interested