AFR heads - roller rockers riding on valve stems crooked?

I was at a swap meet and looking for aluminum heads and found a deal on some AFR's with 1.7 Crane roller rockers - they looked great but I noticed a wear pattern on the roller rocker tips at the valves where some were exactly in the middle of the roller like I would expect and several were no where near the middle of the roller tip - I could easily see the rocker position seemed to be slightly off where the valve end rides was actually not even on the roller part - maybe 15% of it was hanging off - I did not buy the heads because of this and it got me wondering - is this normal? Did valve float cause this? Are the valves bent? Is the head damaged? etc... There were double valvesprings with a damper on them and everything looked to be not that old or used that long - any ideas?

the heads were off the engine sitting on a table - rockers, springs, valves were all still installed -- I was not able to twist the rocker arms at all to see if it would center up on the valve stem tips -- I could see a clear wear pattern on the roller tip of the rocker arm and on the valve stem tip which clearly showed that 10 of the 16 rockers were not even close to being on the center of the valve stem tip - this is the reason I passed on them - I am curious to know what should I be looking at when going for a set of used aluminum heads - I guess I would prefer Edelbrock Peformer street legal heads for low RPM performance 0-60mph.