Preheat oven to 425 °F (220°C). For easier cleanup, line a large baking sheet with parchment paper.
Wash and trim carrots, then pat them dry (peeling is optional). If any carrots are thicker than the width of your thumb, cut them in half lengthwise. Transfer to a large baking sheet, then add oil, salt, and pepper. Toss to coat and spread the carrots evenly on the baking sheet so they’re not overlapping.
Place in the oven and roast for 15-20 minutes, until they are almost tender, rotating the pan halfway. You should be able to somewhat pierce them with a fork, but not all the way through easily.
While the carrots are roasting you can make the miso glaze. In a small bowl, whisk together the oil, miso paste, tamari, sriracha, rice vinegar, agave, garlic, and ginger until combined.
When the carrots are almost tender, remove baking tray from the oven and close the door to keep the oven hot. Now brush each carrot with the glaze and flip over to glaze the other side. Place in the oven for 8-10 minutes. Carrots are done when they are fork-tender, slightly crispy on the edges and the glaze is slightly caramelized. Serve immediately topped with green onions, sesame seeds, and additional black pepper.