In Texas this may be used to describe a white (of anglo descent) person, but it is actually more broadly used to describe a type of bread that Mexican people are known to purchase at local Mexican "panaderias" or bakeries. It is usually eaten with cofee, or can be used for tortas (mexican poor boy sandwiches)
It is not always used in a prejudice way.
"Mija, ve y compra unos bollios para comer con cafe."
"Voy a comprar bolillos para preparar unas tortas."