I would like to know how one can check a wheel for the roundness. Can a invisibly small out of roundness cause vibration? Wouldn't its effect be deleted out when you balance the tire/wheel?

should be able to just spin it and look at the lip for dents. When the tire is getting balanced is a good time to watch for that sort of thing. be sure to check both sides, especially the inside edge. You can also do this by just spinning it on the car (not on a drive wheel though, i.e. use the front on RWD cars). just make sure if you do it that way that its mounted and torqued properly as if you were going to drive on it.

Take the wheel to a good alignment shop. They can measure the inner and outer runout to the nearest .001" on the balancing machine.

Take it to a shop that has the Hunter gsp 9700 balancer.

Yeah, putting it on a balancer is the best (and only) way.

Tire shop ONLY. Balanceing may help reduce the vibration, but if it's bad, it'll have to be repaired or just buy another one/set.

Use a dial indicator with the freewheeling method described above. With this, you can measure runout in thousandths of an inch. Measure lateral (side profile of the lip and radial (inner face of rim hoop) on the inner and outer parts of the wheel. Wihtout a doubt you'll see some measure of runout on all your wheels and how much is too much and causes unfixable balance vibrations, i don't know. Check all your wheels for a baseline and compare values to see if one is radically more than the others.

just take it to a good wheel shop, that way you can be sure.

good info. on how to measure runout/etc. but what are good numbers?
also.. good comment re. measuring against other wheels on the car.. so maybe that answers the question.... but what are people getting on non damaged OEM wheels for runout numbers? I would say form low to high of less than 0.007" would be ok. Just a guess.