Preheat the Anova Sous Vide immersion circulator to 185°F (85°C).
Divide the vegetables and rosemary equally between two large zipper lock or vacuum seal bags. Add 1 tablespoon oil to each bag. Season with salt and pepper.
Seal the bags using the water immersion technique or a vacuum sealer on the moist setting. Place in the water bath and set the timer for 3 hours.
When the timer goes off, remove the bag from the water bath. Heat a large skillet over high heat. Add the entire contents of both bags to the skillet. (Stand back; there will be splatter.) Cook until the liquid is reduced to a syrup, about 5 minutes.
Add butter to the vegetables and toss the vegetables thoroughly. Continue to cook over high heat, stirring frequently, until the vegetables are browned, about 5 minutes. Serve warm as a side for beef, pork, or chicken.
