Heat your oven to 200ºC/Fan 180ºC/Gas 6. Scrub the potatoes in cold water. Slice them into thin rounds about 1 cm thick. Pop them in a large roasting tin.
Peel the onion. Slice it into rounds. Rinse the pepper. Slice into rounds, flicking out the seeds and white bits. Add them to the potato.
Drizzle the veg with 2 tbsp olive oil. Season well with salt and pepper. Bake in the oven for 30 mins. Give everything a stir halfway through cooking.
Rinse the courgettes. Slice them into thickish rounds. Rinse the tomatoes and halve or quarter them.
When the veg has roasted for 30 mins, add the courgette and tomatoes to the tin. Give everything a gentle stir. Roast for another 15 mins or till the potatoes are tender.
Lay the trout fillets on top of the veg. Season with a little salt and pepper. Scatter the almonds over the top.
Pop back in the oven. Cook for another 10 mins or till the trout is cooked through. Serve the trout and vegetables on warm plates with lemon wedges for squeezing.