In my way of thinking I believe that the rails you got are the stock rails that are put on all the Liberties, except for the ones that order the Production Side Rails. I'm not sure that the stock ones would even work/hold up if they were used for a roof rack, etc. Although I may never get a roof rack, I just might get the production rails installed as a just-in-case matter. Same reason I had the trailer hitch installed - may never need it or use it but if I did it's there. Plus, if I ever get rid of our Liberty hopefully the added accessories will add some value to it.
2009 Jeep Liberty
Jeep Remote start
Jeep Liberty Fog lights
Jeep black tube step/side rails
Jeep molded splash guards
Jeep cargo area security cover
Jeep hitch receiver and wiring
Black Taillight guards
My Lib came with roof rails and I bought the Jeep cross bars for $130 I think. Anyway when it comes to roof racks make sure you know what type of crossbars your using I know Yakima and Thule are generic meaning they will work on circular, square and oval. I bought the Yakima Load warrior used for $36 normally it's $276 at an REI garage sale, and had a small scratch on it but all of the hard wear was there except the fairings. I also got a rack extension, roof light mounts and stretch net and love it. I know when Yakima tests their racks and rack mounts they test it at about 4g's
Good luck - Thule is another popular roof rack and there are many others
When you get knee-deep in a situation, floor it.
I was in the same situation you were in a few months ago and I ordered the RRO set up and I love it. http://www.rocky-road.com/kjrails.html very easy to install and very durable. It fits my Thule snowboard rack perfectly and we're looking at getting a basket for the roof in the summers as well. Company was great to work with and the whole set up cost about $300.