And this is probably not easy for a horse, but Roach can sometimes be found doing yoga.
CD Projekt via Laffygas
Roach is such a notorious weirdo that even the developers made fun of her. For April Fool's 2016, they released a video in which they claimed that all the glitchiness was intentional, because otherwise the riding would be "too good." To be fair, when she's not being completely, impossibly wacky, Roach is the fastest horse around. Why, she can even approach Flash-like speeds, as seen here:
CD Projekt via The Therapist Gamer