The foam roller assisted single leg RDL is an excellent exercise to teach someone how to correctly perform a single leg deadlift. This is a beginning level exercise to teach someone the movement prior to loading the movement with weight. The reason why this exercise works so well is it keeps the foot in contact with the hand via the foam roller. This keeps the torso parallel to the ground as a common fault in this exercise is rotating the hips and thorax.
This is an exercise I will use on occasion in the physical therapy clinic with athletes. The multiplaner single leg RDL is a great way to start exploring movement and introducing variability of motion once your typical single leg RDL has been mastered. Start including these variations to develop better body awareness. It also can effectively be used as part of an athletes warmup. Keep a soft knee and stay long through the torso -Torso should be in parallel with the ground
This doesn't take the place of a progressive loading program with your standard single leg RDL. Don't forget the benefits that a progressive resistance program can have on tissue remodeling.