Using the cool setting on the blowfryer helps...but it only solves half of the problem. It's not just the heat that damages the hair - it's the wind.

The motion of your hair blowing in the wind, either outdoors or created by a blowfryer, causes hair strands to rub together and tangle. Wind also dries hair and skin out severely. All of these things can cause damage to the hair. The more often you blow dry, the higher the potential for damage.

As for the greasy roots, some scalps naturally produce more sebum than others. It's true that you can train yours to produce less...to a point. More than anything, the amount of oil that your skin secretes in a day is determined by genetics. So you can't expect to go from greased lightning to "perfect" all of a sudden.

As you age, your hormone levels will change. You may go through phases of oiliness/dryness at different times, so the best thing to do, I think, would be to wash as often as your hair needs it. Find its ideal "comfort zone," if you will, and you and your hair should be able to live harmoniously