Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
On the baking sheet, toss the broccoli florets, sliced red bell pepper, and red onion with 0.5 tablespoons of olive oil, sea salt, and black pepper.
Spread the vegetables in a single layer and roast for 15-20 minutes until tender and the edges are slightly charred.
While the vegetables are roasting, slice the seitan into 0.5-inch thick strips and pat them dry with a clean paper towel.
In a small bowl, combine the garlic powder and smoked paprika, then sprinkle the mixture evenly over both sides of the seitan strips.
Heat the remaining 0.5 tablespoons of olive oil in a large cast-iron or non-stick skillet over medium-high heat.
Add the seitan strips to the pan in a single layer and sear for 3-4 minutes per side until a crispy, golden-brown crust forms.
Pour the tamari into the skillet during the last 30 seconds of cooking, tossing the seitan quickly to glaze and deglaze the pan.
Remove from heat and serve the crispy seitan immediately alongside the hot roasted vegetable medley.