There are a few variables with field rotation such as length of focal length and location of object in the sky to name only two. As JohnG pointed out, drift aligning is the most common way of accurate polar alignment which will in turn resolve your field rotation concerns. CCD or Web came drift aligning will provide greater accuracy than using a illuminated recticle eyepiece as they are pick up drift quicker than the eye can perceive. You can also confirm/correct polar alignment by building an accurate all sky pointing model using software such as TPoint or MaxPoint, however this is typically well beyond most amateurs (generalised statement).
Drift aligning isn't difficult, just time consuming if you want to get high accuracy. 1 or 2 arcseconds from the pole is achievable, but expect to spend a few hours getting there. For a permanent set up, its worth spending the time, but for road warriors carting the equipment around to a dark sky, I wouldn't expect to get this level of accuracy all the time. I'm presently at 15 arcsecs azimuth and 17 arcsecs altitude from the polar (confirmed with MaxPoint) with a permanent set up. I could spend that extra hour to refine it further, but in all seriousness there is no huge gain especially with auto-guided exposures no more that 30 minutes each.
If you don't mind plugging in figures - you can download a field rotation spreadsheet -
http://www.fvastro.org/presentations/FieldRotation.htm