Start by preparing the dough. Warm the milk to about 110°F-115°F and combine with yeast and 1 tablespoon of sugar. Let it foam for about 5 minutes, signaling that the yeast is active. Combine bread flour, all-purpose flour, remaining sugar, and salt in a stand mixer. Gradually add melted butter, eggs, orange zest, and the yeast mixture. Knead with the dough hook on medium-low speed until the dough is smooth and elastic, about 6-8 minutes.
Once the dough is ready, coat a large bowl with vegetable oil, place the dough inside, and let it rise for 1-1½ hours in a warm, draft-free area until doubled in size. For best results, cover the bowl with a kitchen towel or plastic wrap.
Divide the risen dough into two equal parts and shape each into a ball. Create a large ring by stretching the center of each ball, forming an oval about 10½ x 7½ inches. Place the rings on parchment-lined baking sheets, cover lightly, and let them rise for another 45 minutes.
While the dough rises, prepare the sugar paste. Mix egg yolk, flour, confectioners' sugar, and softened butter until smooth. Shape into 16 strips and refrigerate until use. Prepare an egg wash by whisking 1 egg with 1 tablespoon of milk.
Preheat the oven to 350°F. Brush the egg wash over the risen dough and decorate with sugar paste strips, candied cherries, guava paste, and optional almond slices. Bake for 25 minutes, rotating the baking sheets halfway through for even browning.
Cool the bread for at least 30 minutes before inserting the Baby Jesus figurines from the bottom. For added indulgence, slice the Rosca horizontally and fill with whipped cream, pastry cream, or chocolate ganache.
