I have never handheld a rolling shot using anything slower than 1/60th shutter speed... 1/25th is too long and the image becomes blurry and over exposed(depending on aperture settings)
here are a couple of mine at 1/60th handheld, out a window of a moving car at about 40mph.
Edit: I also shoot with shutter priority, I believe it is Tv mode on the canon I use, I don't want to adjust aperture and shutter when I shoot my rollers due to the fact that I shoot in the morning or evening and the light is always changing. Now I am not saying you cannot do rolling shots on full manual mode, but I am suggesting that you save yourself some time and get in more shots instead of messing with the aperture and shutter settings after every 5-10 shots.