Does anyone know why it runs a little ruff while idling, in gear, A/C- on or off ?

Does the engine idle "rougher" than it did when you first bought the car or is it just an observation that the engine seems to run a little rough with electrical loads or air conditioning turned on? A 4 cylinder engine will always be a little rougher than a 6 cylinder and a 6 cylinder will always be a little rougher than an 8 cylinder. The more cylinders the more even the engine will idle. The engine should idle at about 650 to 725 RPM. The idle speed is controlled by the throttle control motor which the computer in your car sees electrical loads, power steering being turned or air conditioning turned on and should compensate by raising the idle speed. A slight vacuum leak could cause a rough idle but not be bad enough to turn on the Check Engine Light. Probably need to plug in a scan tool verify idle speed and see if any data stream information shows a clue as to what is going on.