Preheat your oven to 400°F/205°C, then peel & wash your carrots.
Cut the peeled carrots into ½' medallions, making each piece roughly the same volume as the others, even as the carrot gets thinner. Place the carrots into a large bowl as you cut them.
Drizzle your oil, maple syrup, minced garlic, dried rosemary, salt, and sumac (if using) over the carrots in your bowl, lightly tossing or stirring them as you drizzle. If the fat solidifies because your carrots are too cold, microwave everything for 10 seconds and then resume.
Pour your carrot pieces onto a baking sheet and activate the convection setting in your oven. Put the sheet with the carrots onto the middle shelf in your oven and bake for 12 minutes.
Remove the carrots from the oven and then stir, putting them back in the oven to bake for 6-8 more minutes, until just starting to brown. Remove them from the oven, and enjoy!