Those illustrate the stretched internal shoulder rotators (ISR). The ISR muscles are stretched by external rotation caused by the leg thrust among other motions.
In addition, for the tennis serve the raising up the hitting shoulder, as Roddick has done, according to the Manual of Structural Kinesiology can additionally stretch the ISR muscles.
....the stretch may be increased by abducting the shoulder fully while externally rotated and then laterally flexing and rotating the trunk......
That lateral flexing (of the spine) is what has put Roddick's shoulder up so high.