Breathing and Roll Punching--
I have a question: what about the breathing? When I throw the roll punch, I notice that my breathing seems choppy and my head jumps slightly, any tips?
That's a great question. I'm still working on my breathing, I have the bad habit of holding my breath!
I usually exhale while throwing the roll punch (a combo of three punches). If you do a longer roll punch in the air, or in a drill or practice, that's fine for conditioning, but not realistic.
If you miss your strikes, or they don't have the effect you want, you'll know by the third punch. If you do knock down the guy, then you'll know by the third punch, and if (most likely to happen) your opponent evades your attack, you'll know by the third punch. So I practice my roll punch and breathing (exhale) for a three-punch combo.
Not bobbing your head up and down when striking.
That wastes energy. Shadow boxing and using a mirror will help give you real time feedback. My first suggestion would be to slow down.
Maybe slow down to the point where you are 'effectively' moving, BUT not bobbing your head. Keep drilling this and speed up a little at time.
I will guess you bob you head because you want more power? I know a few other people who do something similar.
If so, focus on your stance. You'll have more power with a better stance.
Many people say holding the horse/goat stance for hours at a time will strengthen you stance. Doing the sil lum tao slowly, also works.
But my favorite drill to strengthen the legs and the stance is a 'modern' one called squats.
Learn how to do a proper squat - knees out, back straight, feet forward about shoulder (or a bit wider) apart, and squat deep. Look online for tutorials.
You can do air squats (a lot of them, but probably not 2 or 4 hours straight), and as soon as you're able, do squats with weight (use proper form to avoid injury and get the maximum results).
If you're bobbing your head because you want to move at lightening speed and you're trying to snap your punches even faster... remember that smooth and efficient moves equals speed. Good timing equals speed. Good footwork equals speed.
So slowing down and making each move count, getting into the proper striking distance, improving your timing, and matching all that up with good balance and penetration so your mass is behind your strikes... will in effect speed you up and give you more power, without forcing erratic speed.
Although not Wing Chun-centric this is a good resource that has changed how I view striking (and kicking). Just note, this is great for finishing moves, roll punching is great for getting in closer.
I hope this helps.