This is a major problem for me and other adult (learner)  gymnasts. In order to round-off , the  leading leg needs to be able to support a deepish lunge position that allows the energy to be transferred forward. Quickly. Then snapped straight, to drive the leg up to catch the other one up.

Its  a problem frequently overlooked and seems to haunt those who have done “proper” exercise. A “proper” exercise lunge ( or the split jerk in Olympic Weightlifting) will demand an upright torso, and probably the heel down on the leading leg.

It is aimed at keeping energy centred, not “rolling it” forward.

You need to be able to direct the lunge forward with a knee bend and not prematurely straighten it.

For now, start building a bit of static “round off lunge” position into your life. It is true that you will never hold the position as the energy is going forward, but when I started to correct this position with my coach, I found that I could not hold this position. I’ll blame a dodgy adductor muscle for now, but the reality is, if I couldn’t hold it, why would I be able to jump into it? The front foot is more on the ball of the foot than the heel, and my shoulders are forward, Neutrali(ish) spin.

Add this to your practice. Once you have it you can begin to turn your upper body away in “proper” preparation of the round off.