You shouldn't be rolling off of a 3 foot drop....
Actually it is acceptable to be rolling off of any sized drop, as long as you find it comfortable.
No, because it's not effecient, I could practically step off a 3 foot drop. Comfortability has nothing to do with it.
And thanks for the clarification Cyanide. 
You should do three-foot drops in both lands and rolls for the first year. No greater than five foot drops. You need to CONDITION your body for these things. You need the technique to be down perfectly. Otherwise, you're not going to be in this for very long at all. And even if your technique's perfect, that doesn't mean your muscles are. If your muscles aren't conditioned, if your tendons and ligaments around your knees and ankles aren't conditioned, then even with perfect technique, you're still causing a lot of stress on your body every time you land.
Danno of PKTO was on a machine that calculated drop force in terms of pounds. He did a sloppy land from one foot up. He got around 500lbs worth of force going down into his legs. He then did a perfect Parkour land from one foot. He still got roughly 250 pounds of downward force. Landing from three feet, you're going to be getting around 350-400 lbs. It's something that our legs can handle, sure. But even with perfect lands, going higher means more force going to your knees. If your muscles can't handle it, then it doesn't matter HOW good your landing technique is. Or your rolling technique. (Rolls disperse the downward force much more.)
Too many traceurs think big before they are prepared for it. They don't even want to try to take things slowly. But if you want to keep doing this twenty years from now, you'll need to play it smart. You're not going to feel the effects, now. But it's happening. Slowly, but surely. And in a decade or two of continuous training... I mean, EVENTUALLY, doing what you're doing, your muscles will get stronger to compensate, but if your joints are damaged already, then they'll keep gettign damaged.
David Belle underwent very specific training for doing jumps and lands. There aren't many disciplines or sports out there that have you train for that kind of thing. Even with a strong background in other things, you may not have developed the right muscles. It will give you an upperhand, though. But just because you might be safer than others because of your background doesn't mean that you should be telling others to practice unsafely.
