Trigger for CA when order submitted?

Could you please pull some kind of trigger (e.g. "free order submitted") when a free order is submitted.

I'm having trouble getting a conditional action to be triggered when a free order is submitted.

I have tried "order updated" - assuming that trigger would fire when the order moves from "in checkout" to "completed" - but the trigger doesn't seem to be detected in the case of a free order.

I am allowing customers to enter a coupon code that gets them free membership. I need to assign a role when that membership order is completed. Is there currently any way I can get that to happen?

TIA