Rollins hates Cap, but he's also fascinated by his 'miracle' body. He also has a medical fetish.

Cue his loving boyfriend/CO arranging a present for him - scheduling a VERY full physical exam for Cap, with Rollins masquerading as his doctor.

Rollins gets to live out his fantasy, Rumlow gets to see a fascinating (and fucking weird) side to his boyfriend, and Steve just suffers through a series of humiliating and painful procedures.