Preheat oven to 375°. Line a rimmed baking sheet or baking dish with foil.
Toss the hulled and quartered strawberries with the granulated sugar and place on the foil-lined sheet. Roast for 20 minutes until the strawberries are softened and there is some strawberry liquid on the tray.
Remove from the oven and pour the liquid into a small dish; then, scoop the strawberries into another bowl. Set aside.
Line a muffin tin with paper liners.
Prepare the muffin mix according to package directions. At the end, pour in the roasted strawberries and the strawberry liquid and gently fold to combine.
Scoop evenly into the lined muffin tins and bake for 20-25 minutes until lightly golden brown.