In a small bowl, whisk together maple syrup, balsamic vinegar, oil, soy sauce, paprika, and red pepper flakes. Place sliced tempeh in a sealable container and pour marinade over tempeh. Place in fridge for at least 30 minutes or up to 12 hours.
Preheat oven to 400F. Option to line large baking sheet with parchment paper to make for easier clean up (highly recommend!)
Place cubed sweet potatoes in a large mixing bowl and set aside. Cut ends off of brussels sprouts and cut in half. Place in bowl with sweet potatoes then toss with 1 Tbsp olive oil and sprinkle of salt and pepper. Spread veggies onto large baking tray, arranging brussels sprouts with cut-sides down. Next, place marinated tempeh slices on baking sheet – do not pour out marinade! Set remaining marinade aside.
Place baking sheet in oven and cook for 10 minutes. After 10 minutes, flip sweet potatoes and tempeh. Return baking sheet to oven and cook another 8-10 minutes, or until brussels sprouts and sweet potatoes are soft when pierced with a fork. Remove from oven and set aside.
While tempeh and vegetables are roasting, place buckwheat groats and water in a medium saucepan over high heat. Bring to a boil and then reduce to a simmer. Cover and gently simmer for 15-18 minutes, or until soft but still chewy.
When ready to serve, evenly divide cooked buckwheat, tempeh, and roasted vegetables between 4-5 bowls. Drizzle remaining marinade on top and enjoy!