Are there any overtime rules for official Riftbound events?

Ruling: Yes, when round time is called, players complete 5 more turns, and at the end of the 5th turn after time was called, the higher score wins (draw if tied).

Sequence:

• Round time is called
• Players complete 5 additional turns
• At the end of the 5th turn, compare scores
• Higher score wins; draw if scores are tied