My easiest is chicken. All done at the same time, oven timer on.
Top shelf- Large chicken in a large tin with chopped onions, celery and an inch of water.
Middle shelf- baking tray with large chunks of potatoes and parsnips and some fat from the previous roast.
Bottom shelf- chunks of courgette, mushrooms, fennel, carrot, whatever.
The bottom shelves are really close together so the veg cooks more slowly.
Oven on 200 for 90mins, no preheat.
At the end, get the chicken out onto a board or plate to rest. Check the veg and potatoes, rearrange in the oven and give them another quick blast if necessary.
Pour the liquid and veg from the chicken tray into a jug. Skim off the fat for next week's potatoes and make gravy from the veg and juice (stick blender).