Turbulence vs Computer glitch
If, as some posters are suggesting, this incident was caused by a computer failure, this would imply that the “violent” roll reversals were caused by movement of the control surfaces. Although it is not possible to know how violent these reversals were, anecdotal evidence suggests that they were well above that which is possible to induce via the control surfaces. This would support the hypothesis that this incident was initiated by some sort of turbulence related upset.