Preheat the oven to 375°F and prepare a muffin pan with liners.
Slice the strawberries and place them into a skillet over medium heat. Roast the strawberries in the pan, flipping and stirring occasionally to evenly heat them. Once they have softened, have released their juices, and can easily be broken down, remove them from heat. Use a fork to gently mash them, leaving a few chunks. Set aside to cool.
In a large bowl, whisk the flour, baking soda, baking powder, and salt together. These are your dry ingredients.
In a separate bowl, whisk together the oil, sugar, eggs, vanilla for about a minute until very smooth and creamy. Then add the mashed banana. These are your wet ingredients.
Make a well in bowl with your dry ingredients and pour in all of the wet ingredients. Use a whisk to stir just a few times to bring the batter together, until the flour is just combined. Lumps are okay here--do not overmix.
Gently fold the roasted strawberries into the batter.
Divide the batter between each cup in your muffin pan.
To make the streusel topping, use a fork to stir all of the ingredients together until you have a slightly moist, crumbly mixture. Then crumble it over each muffin before baking.
Bake for 22-25 minutes, or until muffins are set and a toothpick comes out clean.
To make an icing to go on top, whisk the milk and powdered sugar together until smooth and drizzle over the muffins.