my quick $.02 ...
I picked up the aforementioned Rogue Gemini for "muscle smashing" along my spine and it helps keep things loose along my spine from rucking, lifting, and running. I also use a hard softball on all my tight spots as well and have actually cut back on my yoga and static stretching as a result of doing more rolling and muscle smashing. I've also used PVC pipe (+/- 3 or 4" diameters) as a foam roller and it'll really do the job. Some use racquetballs but I don't feel that I get the same pressure plus they get caught up under my clothes which the slippery softball doesn't seem to do.
I can't say if this has made me any "faster" as I've been gradually but increasingly integrating it over the last few months but I can say that I am stronger and feel a difference in strength, movement, overall flexibility, and recovery. ...which one could rationalize would allow you to train more, and at higher intensities... etc, etc.
I'm new here and don't want to plug products but since we're talking about mobility and how it affects one's training, the book "
Becoming a Supple Leopard" is definitely worth a read if you're interested. The author also has a pretty good u tube channel.
...now back to PT. Train hard fellas!