Pour the rosé wine into a mixing bowl and stir in the sugar until fully dissolved, creating a sweetened wine base.
Add the freshly squeezed lemon juice to the mixture for a bright, tangy note, then give it a gentle stir.
Transfer the mixture to a shallow freezer-safe container, spreading it out evenly for quicker freezing.
Place the container in the freezer and let it chill for about 2 hours, stirring every 30 minutes with a fork to break up ice crystals and encourage a smooth, slushy consistency.
Once the mixture is mostly frozen with a slushy texture, give it a final stir to break up any remaining large ice chunks.
Serve the rosé slushie immediately in chilled glasses, garnished with fresh berries or herbs if desired for extra color and flavor.