IMO, roost shooting a gobbler is WAY worse than shooting a duck on the water. Ducks are hunted over decoys spreads. Shooting one with his feet 3 feet off the water versus shooting one after he lands is a somewhat arbitrary distinction. It definitely eliminates the wing shooting aspect, which is part of the sport, but I'm not getting worked up over it if someone does it once in a while.
Roost shooting a gobbler is no better than spotlighting a deer. They are, by instinct, much more vocal on the limb because they are safe from every natural predator except horned owls. To figure out the exact roost location of a gobbling turkey in the near darkness requires only the ability to hear. You can't sneak up to every roosted gobbler. If you wanted to try it in some of the open cypress woods I hunt in early spring, good luck. But in many situations and in many landscapes, all you have to do is walk slow and keep a tree between you and him. Even if he sees you, his instinct is to go quiet and hunker down until the threat passes. When they flush from the roost, it is almost always when you get 30-40 yards from them in the tree. So a roost shooter just takes advantage of those natural instincts to get a cheap, quick picture of a dead gobbler. And that's not even accounting for the fact that you can roost one the night before, walk in in the dark, sit down 15 yards from his tree, point your gun up, and wait til the clock strikes shooting time.
Roost shooting summarily dispenses with every shred of sport and skill and respect for the animal in exchange for a dead turkey with a lot of roughed up feathers.
I took a kid on the juvenile two years ago. We set up in the dark and at daybreak a turkey gobbled above his left shoulder, 2 trees over. He's 9, loves hunting, and BADLY wanted to kill a turkey to show up his older brothers. I wouldn't have let him shoot it, but he didn't try. Later that day — after calling a group of 2 year olds gobbling through a cypress stand — I asked him about the roost turkey. He just said "I didn't want to kill one like that."
For the record, I could not possibly care less whether there is a rule provision specifically prohibiting roost shooting. There are some things you shouldn't have to be told not to do.