In a saucepan, bring barley, water, salt, and butter to a boil. Reduce heat to a simmer. Cook covered until tender and most of the liquid has been absorbed, about 40 to 50 minutes.
Make the vegetables - On a sheet tray, add all vegetables in their own sections. Drizzle with oil and sprinkle with salt, garlic powder, cumin, and pepper. Mix seasoning on vegetables.
Roast for 30 to 35 minutes, until vegetables are tender.
Make the sauce - On a cutting board, place the scallions, fresh parsley, and fresh mint and pack them together and add a sprinkle of salt. Then start chopping so the herbs are finely chopped for the sauce.
In a small bowl, add the chopped herbs, yogurt, olive oil, lemon zest and juice, and a pinch of salt. Mix well. Place in refrigerator until ready to use.
To assemble - In a bowl, add barley, then roasted vegetables, and green goddess gremolata dressing. Top it off with toasted pumpkin seeds. Enjoy!