Add the brussels sprouts to a sheet pan and toss them in the olive oil, salt and pepper. I like to roast mine directly on the sheet pan with no parchment paper, so I grease mine with a little cooking spray.
Roast them for 25 minutes.
In a small bowl, whisk together the miso marinade until thick. After 25 minutes, remove the brussels sprouts from the oven and spoon half of the sauce over them, and toss together.
Place the sheet pan back into the oven and roast for another 10 minutes.
When ready to serve, pour the remaining sauce over the brussels sprouts.