Well if you are like me I purchased my 2008 nitro fully loaded with all the bells and whistles. The roof rack system is totally different then the 2007.
2008 model trim is not ornamental. Your sport utility bars come with the rails that fit onto the roof. Extremely easy to put on it took 20 minutes. Take off 4 bolts put in the track skrew track bolts back down, repeat for other side. Slide on the cross members and tighten down with tool provided in the kit.. done. I have added the link to show you how it looks. Just give your dealer a call and order the part number I have given you.
Part from mopar is #82211487 This is the rails that have special fittings on them to go onto 2008 model. Just call your dealer and give him the part number. He may have told you replace it with the 2007 trim and bars.
I would not reccomend this since there are issues with the 2007 system.
LOVE MY NEW SUV a real compromise between a van and a truck.
They have changed the system for 2008 because the 2007 models have had so much problems with lifting and noise.
Once your sport utility bars are on you are set to add a carrier of your choice on your roof. I personally feel they should have included it with the model as they did on the 2007's Dodge-Nitro.Com - Dodge Nitro Forum - PhotoPlog - sport utility rack for 2008 nitro
It took me some time to find out this information for you and I am off today to get my bars so I am going to put a bag carrier on the roof for camping and in the future it leaves the door open for a different carrier in the future.