Heat oven to 400 (200C) and line 3 rectangular baking or cookie tarys with parchment paper. Spread the sweet potato out over one tray, the cauliflower out over another and the broccoli over the other. Drizzle olive oil over the vegetables and season with salt and pepper.
Place the trays into the oven together if your oven space allows or cook in batches. Cook for around 15 minutes until just cooked, removing the trays from the oven and giving each vegetable a quick stir around half way through. Allow to cool to room temperature.
Place the sunflower seeds in frypan or skillet and dry roast over a medium heat for a few minutes whilst gently shaking the pan, until they have browned up nicely.
Once the vegetables have cooled place them in a large mixing bowl and gently mix through the basil pesto taking care not to mash the vegetables together. Check the seasoning and adjust if required.
Transfer to serving bowl or dish and sprinkle over the toasted sunflower seeds.