I started a forum just like this that I forgot about and this is what someone replied to it. Definitely sounds like an evaporative emission system problem, most other things i can think of wouldnt cause a rough idle only after filling up. I'd say you most likely have a soaked charcoal canister if you always put more gas in the tank after the pump stops. The charcoal canister is connected to the tank to absorb the vapors from the gas when it evaporates. If you overfill the tank, liquid gas can get into the canister and soak it which usually causes problems starting or rough idle. You can replace these pretty easily, its right under the rear in a black box on the spare tire well if im not mistaken. But if it idles rough every time you fill up regardless of how much it could be a stuck open purge valve. usually the vapors from the canister are purged during hwy driving, but if the valve is stuck open when you put gas in the tank the expanding vapors from filling up can push the liquid fuel in the canister into the intake causing it to idle rough for a bit. once you start driving the o2 sensors and fuel trims account for the rich condition and it will go away