Spinedoc,

The "roll" to one side or another on uneven roads" you mention is called "tramlining" and is a natural consequence of very wide tyres. It is normally kept to acceptable levels by carefully balancing the various aspects of the front suspension and steering geometry.

This delicate balance can be screwed-up if the offset is wrong (as Luke says). If you want the wheels to look as wide as possible, there's a price to be paid (not just in dollars).

__________________
Paul Gibbons
'93 320CE
'73 Jensen Interceptor (Resting)
Giant Full Sus Mountain Bike