If the yaw is finished there is no more roll - if you are "holding the yaw
with rudder" you are still yawing
No. The aircraft is yawed ie not travelling in the direction it is pointing, but it is not yawing further (which it would have to be doing for one wing to be flying faster than the other). And the yawed aircraft experiences the rolling force that the OP is trying to understand. Go and try it sometime - you end up flying straight and level with crossed controls (side-slipping, as has been said).
The rolling force comes from a number of effects as has been explained, of which the dihedral effect is the greatest in a light aircraft - even though the amount of dihedral is only a few degrees.