How much of the grist would you smoke? All of it, or just your bulk of what makes the grain bill?
If you are doing all-grain, I smoke all the pale malts. Specialty grains and darker roasts will not pick-up as clean a smoke flavor and don't need any more roasting than they already have. Controlling the smokiness with time and amount of smoke is much easier than trying to balance amounts of smoked vs. un-smoked grains IMHO.