Preheat oven to 400 degrees. Line a very large baking sheet with parchment paper and set aside. Use two pans if yours are not large enough.
Combine sweet potatoes, brussels sprouts, oil, salt, pepper and garlic in a bowl and toss to coat evenly.
Spread in a single layer on one half of the baking sheet.
Arrange tempeh on the other half of baking sheet, reserve marinade.
Bake for 15 minutes and flip vegetables and tempeh. Brush tempeh with more of the reserved marinade.
Continue baking for 15 minutes longer or until potatoes are tender and brussels have browned.
Once baked stir the vegetables and tempeh together to distribute well.
Serve as is or add tofu scramble and toast for breakfast or your choice of grain and fresh salad for dinner.