Preheat oven to 400 degrees Fahrenheit. Line a baking sheet with a silicone baking mat or parchment paper and unroll the pie crust on top. Bake for 12-15 minutes or until golden brown. Remove from the oven and set aside to cool.
To make the blackberry mixture:
Add the blackberries, sugar, and lemon juice to a small saucepan over medium heat. Cook for 5-10 minutes or until the blackberries start to soften and release their juices. Mash well and transfer to a small bowl to cool.
To make the ice cream:
Using a hand mixer or stand mixer fitted with the whisk attachment, mix the sweetened condensed milk, heavy whipping cream, and vanilla until thick (about 4-5 minutes).
Break the cooled pie crust into small pieces and gently fold it into the ice cream mixture.
Layer the ice cream with spoonfuls of the blackberry mixture into a loaf pan and gently swirl with a knife.