I am not sure about the rattle but I had a similar leak in my '08. According to what I've read, this could either be a leak around your roof rack bolts, or water is getting under the rubber seal around your hatch door. In my case it was the latter. I pulled the rubber seal off from about 9:00 to 3:00 (if you think of the hatch opening as a clock face), and then used a good amount of RTV silicone to seal it back on. I did check the roof studs and the welds around the hatch too though. You can pull off that center trim piece by pulling down in the center. Once the metal clips disengage, you can dislodge the tabs on the left and right sides and take it off (the half cup of water pools in this trim piece, by the way). From there you can see above the headliner with a flashlight and see if water is coming in through the roof rack stud area. Good luck!
2008 Liberty Sport 4x4 Automatic