Preheat the oven to 350°F. Line a baking sheet with parchment paper. Add the flour, brown sugar, rosemary, sage, cinnamon, and salt to a bowl. Mix until the ingredients are evenly combined. Add in the cold, diced butter.
Use your fingertips to pinch the flour and butter together. Alternatively, you can use a pastry cutter. Continue to work the butter into the flour until you get a mixture that resembles wet sand. It should come together when you squeeze it in your fist, then crumble into round clumps when you break it apart.
Allow the mixture to fall apart into crumbled pieces then transfer it to a baking sheet lined with parchment paper. Spread the crumble evenly out onto the baking sheet. Bake it in the oven for 12-15 minutes until golden brown and crunchy. Mix halfway through baking. Remove the crumble from the oven and allow it to cool to room temperature. Break apart any clusters that have stuck together.