Question: When do you buy a rosca de reyes?
Disambiguated questions and answers: question: When and for what do you buy a rosca de reyes?
When do you buy and eat a rosca de reyes?
answer: Día de Reyes
to celebrate Epiphany
Kings' Day
January 6
question: During what celebration do you buy a rosca de reyes?
On what date do you buy a rosca de reyes?
answer: Epiphany
January 6
Natural Questions answer: January 6 (from the Wikipedia article "Rosca de reyes")