He said tennis ball, which is what I use. I roll the scapula, but not on the floor. I'm up against the wall so I can control the pressure. The fossa is filled with the infraspinatus, which clinically carries a lot of junk. I move the ball all over the fossa, and then roll it out to the posterior delt/capsule. I seem to always get some good hits. Reversing that and rolling the pecs next is a nice little sequence, you just look a little silly with your face pressed up against the wall like that.
"And if a frog had wings it wouldn't bump his ass a hoppin'!"
- The wisdom of Nathan Arizona