I found this article by 5 Rings Athletics an excellent synopsis on what exactly hip retroversion and hip anteversion is. Why trying to improve one in a patient and athlete may be futile and why your athletes and patients may actually be hurting themselves if they are going against their anatomy to try to improve a perceived lack of ROM.
A Case Study of Femoral Retroversion
An anteverted hip wouldn't want to be trained into external rotation. For example, don't sumo deadlift with an anteverted hip.