Why does everyone who does the shoulder roll have their lead hand down?

[HtotheZ]

Everybody I've ever seen use the technique has their lead hand either all the way down or wrapped around their torso. Is there any particular reason for that? Can you use the technique with your lead hand still up?

[Rockin']

the down hand protects the ribs and the belly............ Rockin'

[Bird1]

If you are fast it's more difficult for your opponent to see the jab coming aswell when you have your hand low. But I think it's a good idea to switch it up, you often see Mayweather use a high guard.

[Beavis_5000]

Bernard Hopkins I believe uses a shoulder roll but not with a philly shell style.

I think its more common for someone who uses a shoulder roll to use a philly stance because your hands are in better position for a counter in the philly.

Also dropping the lead hand leaves that opening to draw in the punch so you can shoulder roll and counter.

[ShoulderRoll]

the down hand protects the ribs and the belly............ Rockin'

Exactly, the arm is kept down to protect against body punches.

[LoadedWraps]

Everybody I've ever seen use the technique has their lead hand either all the way down or wrapped around their torso. Is there any particular reason for that? Can you use the technique with your lead hand still up?

Sort of, but the shoulder roll is largely part of what's known as the philly shell defense. As an amateur fighter I use both the philly shell and a more orthodox mexican style stance similar to Marquez when fighting, the shell defense I feel more comfortable in when under alot of duress because I have better balance and weight distribution with my lead hand down and my ability to roll and flow between defensive slips, rolls, and punches is much faster, the jab and hook as just as fast as from a peekaboo stance if disicplined as such, and the body defense is excellent. I do raise my lead hand and go to a peekaboo stance now and then to confuse my opponent and because I can throw several quick combinations I work on constantly from several positions with my hands up high and close, you have to be able to adapt.