I'm not saying it can't be done, since I've never tried it. I'm not sure how well that would work though...
They do make prebent sections though if all you need is a 90...
http://www.mcmaster.com/#strut-channel-systems/=t7iy4r
About $100 a section, wow. I would think there would be some way to bend it and still have the rollers work.
