Preheat the oven to 350℉. Line a large sheet pan with parchment paper or a silicone baking mat and set aside.
In a large bowl, stir together the flour, oats, brown sugar, baking soda, and salt.
Melt the butter and allow it to cool to room temperature, so it doesn't melt the sugar and cause greasy cookies. Combine with the vanilla extract and egg. Pour into the dry ingredients. Stir until a thick dough forms. You may need to knead the mixture with your hands.
Cover and refrigerate the dough while you unwrap the Rolos.
Take about 3 tablespoons of dough and flatten it in your hand. Place two candies in the center, then fold the edges of the dough up around the candies, sealing them completely to form a large cookie. The dough should just cover the Rolos without much extra. Make sure none of the candies are exposed or the caramel will leak out during baking.
Place 6–8 cookies on the prepared sheet pan, giving the cookies plenty of room. Refrigerate the tray for 10 minutes to firm up before baking.
Bake for 9–12 minutes. I love to underbake these just slightly, it creates a softer cookie with melted and gooey caramel. Overbaking will cause the caramel to harden when cooled.
Allow the cookies to sit on the cookie sheet for another 2–3 minutes, and then transfer to a cooling rack to allow them to firm up a bit.
To top with chocolate, combine the chocolate chips and vegetable oil in a microwave-safe bowl. Microwave in bursts of 15 seconds, stirring in between each burst for 10 seconds until completely melted.
Dip a spoon in the melted chocolate and drizzle it over the cookies. Alternatively transfer the chocolate to a small plastic bag, snip off the top with scissors, and drizzle all over.
Notes
Storage: Store baked cookies in an airtight container at room temperature for up to 1 week. Freeze dough balls and bake them directly from the freezer.