Go to 1010tires.com and lookup the tires and sizes you are interest in. They will usually list how many revs-per-mile. Or, you could do it the low tech method: measure the tire's height, multiply by Pi (3.141592) to arrive at the revolution distance in inches. Then divide figure that into how many inches there are in a mile (5280 x 12). There's your answer.
If you want to find it out for a tire size you don't have, use one of many tire size calculators to arrive at the tire heigth and subtract one inch for compression. The calculation for your mentioned tire size is 30.6 inches, in reality it would measure 29.6 inches high installed on your truck.