Cut the romanesco into small roses, cut the roasted carrots and potatoes into 2 cm cubes. Cut the leek into rings and grate the cheese on a rösti grater.
Melt the butter in a frying pan, add the carrots and steam over medium heat with the lid closed for 10 minutes. Add the potatoes and steam for 5 minutes, then add the romanesco and leek and steam for another 10 minutes. Season with salt and pepper.
Add the spaetzli to the vegetables and cook for 5 to 10 minutes, turning carefully. Before serving, add the cheese.