The thing about tray bakes is that you can look in the fridge, take anything un-busy, add some spice and dinner is done!
Some mixes I like though are:
Peppers, courgettes, onion, baby tomatoes (with herb mix)
butternut, sprouts, onion (with lemon pepper mix)
potato, peppers, pumpkin, onions (with chipotle mix)
butternut, chickpeas, onions, goat cheese (with honey mustard dressing)
I cook the protein separately.