I know you are more interested in a rack than a basket, however I made a basket using two of these:
http://www.harborfreight.com/atv-cargo- ... 67623.html ...
Take two of those cargo carriers, bolt the rack halves to a strip of 1/8" X 1" steel, with the two racks facing each other, and you now have a roof basket! I got the idea here :
http://www.jeepforum.com/forum/f11/budg ... t-1089244/ I had to mount my homemade roof basket with the cross bars of the "floor" running at a right angle to the roof rails of the Jeep, instead of parallel with them like the one shown in the link; using some homemade brackets and 2" muffler clamps (My Liberty is a Renegade).
I've added some aluminium square tube, where the one shown in the link has a "valley", as well as a welded in cross bar to securely carry some gas cans... With that basket I've also hauled camping gear, lumber, electrical conduit, etc...
After mounting my homemade basket on my Jeep I thought it's really boxy shape didn't go well with the more rounded shape of the Liberty, but it has really grown on me. I've had several people comment on it, saying that they like it. One of my co-workers asked where I bought it; when I told him that I made it using two ATV hitch carriers he said that he wanted one for his Baja Bug...