Preheat oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Place pretzels in a zip-top bag and crush them with a rolling pin until roughly broken.
Combine crushed pretzels, melted butter, and granulated sugar in a bowl, then spread evenly on the prepared baking sheet.
Bake the pretzel mixture for 8 to 10 minutes or until deeply golden brown, tossing halfway to redistribute butter coating.
Allow the roasted pretzels to cool and crisp at room temperature.
Generously butter the interior of a 8x8-inch baking pan.
In a large bowl, combine crispy rice cereal, freeze dried strawberries, roasted pretzels, and additional mini marshmallows if using.
In a large pot over medium heat, melt 1/2 cup butter with the 10 oz bag of mini marshmallows, stirring continuously until smooth.
Remove from heat and stir in vanilla extract and kosher salt.
Fold the dry mix into the melted marshmallow mixture, ensuring all ingredients are evenly coated.
Transfer the mixture to the prepared pan and press firmly into an even layer using greased hands or a spatula.
Allow treats to cool and set at room temperature for about one hour before slicing into squares and serving.