Freeze raspberries in a single layer on a cookie sheet.
Prepare and bake brownies according to package directions. Cool brownies completely on a wire rack. Cut into small chunks.
Combine brownie chunks and softened ice cream; stir until brownie is evenly distributed. Add raspberries; stir gently. Serve immediately, or transfer mixture to a freezer-safe container and freeze until ready to serve. Let soften at room temperature 5 minutes before serving.