My developers are only "on call" in the sense that their code supports responders who save lives.

In that context, I maintain the expectation that I might call any of my developers at any time.

That said, I have made that call once ever in the years since I built this team, and it happened to be during business hours anyway.

Officially, I require my team members to take off time to make up for any overtime worked. (Only officially, I guess, since it has not been tested.)

Our flexible work schedule already sets an expectation that someone too tired to work should let their manager know and sleep in and come in later. That has been tested, for various personal reasons. So that would still apply for a late night or early morning incident.

I'm not able to pay an overtime rate, at this time.

I credit my prioritization of graceful rollback for some of the lack of actual on-call calls. But lots of credit is also due to our fantasticly skilled first line responders.