Crush the Raspberries: Pulse the freeze-dried raspberries in a food processor or blender until they form fine crumbs. Set aside.
Melt the Chocolate: In a microwave-safe bowl, combine white chocolate and butter. Heat in the microwave on medium-high in 30-second intervals, stirring between each until fully melted and smooth. Be cautious not to overheat.
Mix and Chill: Add the rosewater and ground raspberries to the melted chocolate. Gently whisk until blended, being careful not to incorporate too much air. Cover with cling film directly on the surface of the mixture and let it cool to room temperature. Once cooled, refrigerate for 2-3 hours or overnight to firm up.
Form the Truffles: Use a small cookie scoop or your hands to form 1-tbsp sized balls of the truffle mixture. Roll each ball in powdered sugar until fully coated. If the mixture becomes too warm and difficult to handle, refrigerate again until it firms up.
Chill and Serve: Place the coated truffles on a lined plate or tray and refrigerate for 30 minutes to 1 hour until firm. Serve chilled.