Make the tangzhong by combining the milk and the flour in a small saucepan and whisking until there are no lumps left.
Place the saucepan over medium heat and cook the mixture, stirring regularly, until it has thickened to a paste. This should take about 1-3 minutes.
Add the tangzhong to a large bowl or a bowl of a stand mixer. Add all of the ingredients of the dough to the bowl and mix to bring the ingredients together.
Knead the dough for about 10-12 minutes using a mixer or about 15 minutes by hand until it is smooth and elastic. Shape the dough into a ball and place it in a bowl and cover.
Let the dough rise until puffy, about 60 to 90 minutes.
While the dough is rising, make the pesto by adding the tomatoes, crushed red pepper, parmesan cheese, and salt to a food processor. Pulse until the tomatoes are minced and the cheese is evenly combined with the tomatoes. Add the oil little by little until the mixture is a paste and is easy to spread. You may need more or less oil depending on the consistency you prefer.
Transfer the dough to a work surface and pat it into a 10”x12” rectangle about ½” thick. Try to pat the dough into an actual rectangle with corners instead of an oval to get even rolls.
Spread the pesto evenly over the dough, covering everything but a ½” strip along one long side. Sprinkle the mozzarella cheese over the pesto.
Starting with the filling-covered long side, roll the dough tightly into a log.
Cut the log into 1-in equal pieces. Cut the dough using unflavored floss or a nylon thread to get a clean cut. If you have neither, use a sharp knife.
Place the rolls onto a parchment lined baking sheet, leaving about 2-in of space between each one. Tuck the ends of the spirals underneath the rolls to prevent them from unraveling.
Cover the rolls and let them rise for 30 to 60 minutes. The rolls should be puffy and shouldn’t bounce back immediately when gently pressed.
While the rolls are rising, preheat the oven to 375 F.
Bake the rolls for 15-20 minutes until they are lightly brown on the tops and the cheese is melted. Serve hot.