We don't eat the rosca, whatever, I think that's Mexico...
Before the US came here, we only gave presents on this day, January the 6th, the day of the Epiphany, to commemorate when the Three Kings (or the Magi) gave their presents to the infant Jesus. We put grass under the tree (before, we didn't use trees, I think) so the camels can eat (same as the cookie for Santa) and we get presents.
Sadly, now that we have Christmas the American way (with Santa Claus), then we have the best presents on Christmas and the second-rate ones on Reyes, our parents saying that they have less money... Yeah, kings have less money than a fat bastard with a beard, riiight. ><
It's a wonderful tradition, and it means we get presents twice during the season, always a plus, lol.