Good luck with that. You and only you sign the statement. There are a few things that happen following an incident, you get D&A tested, you get asked if you had sufficient rest and if you’ve had your break was it at the right time within the diagram and for the correct length. If you’ve done something really bad I doubt the manager would convince the RIO they were to be as culpable as you, more likely show them that you’ve booked on as fit and ableIt is a split responsibility, you are signing that you are fit for work but a manager should not let you work, and would certainly not be considered blameless following an incident.