The bonus from rod of the pact keeper, +3 (and other rods of the pact keeper) is not applied to cantrips gained from the Pact of the Tome warlock feature. The feature say that, even if they do not appear on the warlock spell list, the cantrips are nonetheless warlock spells for the character. The bonus from the Rod of the Pact Keeper should apply to them.
Hello,
The bonus from rod of the pact keeper, +3 (and other rods of the pact keeper) is not applied to cantrips gained from the Pact of the Tome warlock feature. The feature say that, even if they do not appear on the warlock spell list, the cantrips are nonetheless warlock spells for the character. The bonus from the Rod of the Pact Keeper should apply to them.