Preheat the oven to 180 C.
Chop the mushrooms in half, the peppers into slithers and leeks into small chunks. Place them in a roasting tray and cover with avocado oil, salt, pepper and thyme.
Roast in the oven for 40 minutes until golden and cooked through.
Mix the olive oil, lemon juice and a pinch of salt together and mix through the salad leaves.
Pop the warm veg on top and dig in!