Bring a few inches of water to boil in a pot and fit the pot with a steamer basket. Place the tempeh cubes in the basket and steam for 10 minutes.
Whisk together the tamari, broth, vinegar, syrup, garlic, ginger, and red pepper flakes. Place the tempeh cubes in a glass storage container with a tight-fitting lid. Pour the marinade over the cubes. Cover the container and shake gently to distribute the marinade. Transfer the container to the fridge and allow the tempeh to marinate for at least 2 hours, or up to overnight.
Trim the stem off of the broccoli crown(s). Cut the crown into bite-sized florets and pieces.
Preheat your oven to 400F. Line a baking sheet with parchment, foil, or silpat, or use a non-stick baking sheet. Remove the tempeh cubes from the marinade, reserving the marinade. Arrange the cubes on half of the baking sheet. Arrange the broccoli on the other half.
Pour 1/2 cup/120ml of the marinade over the tempeh and vegetables. Reserve the rest of the marinade for drizzling over the finished recipe.
Roast the tempeh and broccoli for 30-35 minutes, or until the tempeh is crispy and broccoli is browning. Flip the tempeh cubes and stir the broccoli on the sheet once halfway through cooking.
Serve the tempeh and broccoli over cooked rice or noodles. If you like, drizzle a little extra marinade over the dish before enjoying.