I am not saying my approach is correct, but it has served me so far. I don't really pay attention to rim width. I started riding in 1991 on mountain bikes. I had the standard Smoke and Dart in the 2.1 and 2.2 widths on fairly narrow rims. I never had a problem with tires rolling off the rim. My riding style was much wilder then than it is now so the prospect of putting a 35 on a standard road rim does not even rise to the level of concern. That being said, if I was setting out to buy or build a nice wheelset, rather than finding a good deal on a used set, I would go with a wider rim.