Preheat the oven to 350℉ (177℃). Prepare baking sheet pans with silicone baking mats or parchment paper sheets.
In the bowl of a stand mixer fitted with a paddle attachment or in a large mixing bowl with an electric hand mixer, cream together the unsalted butter, light brown sugar, and granulated sugar until smooth and creamy. Add in the eggs, molasses, and vanilla extract and mix until smooth.
Add in the old-fashioned rolled oats, all-purpose flour, ground cinnamon, baking soda, and salt and mix on low speed until the cookie dough forms. Fold in the raisins until well dispersed throughout the cookie dough.
Portion the cookie dough using a large cookie scoop (3 tablespoons). Place the cookie dough balls on the prepared baking sheet pans, allowing room for spreading. Press additional raisins into the tops of the cookies, if desired.
Bake the cookies for about 11 to 12 minutes until slightly golden-brown on the edges. Remove the pan from the oven and allow the cookies to cool on the pan for about 2 minutes. Transfer the cookies to a wire rack to cool completely.