Cut tempeh into cubes, slabs, or quarter-inch slices — thinner cuts crisp faster, thicker pieces stay meatier. Mix tamari, vinegar, and any seasonings (garlic, ginger, sesame oil, hot sauce, or coriander) in a shallow nonreactive dish. Add tempeh, turn to coat, and marinate at least 20 minutes at room temperature or up to 2 days in the fridge. Preheat oven to 400°F about 15 minutes before cooking.

Preheat oven to 400°F. Arrange marinated tempeh on a nonstick or lightly sprayed baking sheet with generous space between pieces — crowding causes steaming, not crisping. Use two pans if needed. Place on the center rack. Roast 12 to 15 minutes, flip once, then roast another 8 to 13 minutes. Total time is 20 to 28 minutes depending on thickness and marinade. Thinner slices finish near 20 minutes; thicker cubes may need the full 28. If edges brown too fast, reduce heat slightly or raise the rack.

Tempeh is done when the exterior is deep golden brown with crisp or slightly charred edges and a dry, set surface. There is no target internal temperature — judge by color and texture alone. Rest pieces for 2 to 3 minutes after pulling the pan so the crust firms up. Serve immediately for best crispness. Do not pull it early; pale, soft tempeh lacks the roasted depth this method is meant to deliver.