I have been getting the same 3 items from my rerolls when they are suppose to lock out after I got them. I now have 4 rotmire rings, 3 pants, and 2 trinkets and have yet to get any of the other items from rerolls.
My rerolls have been wasted.
What items specifically are you looking for, and which character?
And also note that the items are for each tier too. You can bonus roll on LFR, Normal, and Heroic and get the same item all three times since they have different tables.