- Pre-heat oven to 180°C.
- Place prepared vegetables in a single layer on a large roasting tray lined with baking paper. Spray with olive oil and season with salt.
- Roast for 25 minutes until just tender.
- Meanwhile heat butter in a medium saucepan then add flour and cook for 2-3 minutes or until pale golden and sandy in texture.
- Simmer milk and saffron for 2 minutes to release the flavour and colour. Gradually add milk to the flour mixture, stirring constantly until smooth and thickened.
- Stir in Mainland Colby Finely Greated and saffron threads and cook a further 2 minutes then season to taste.
- Spoon the cheese sauce over the vegetables and top with extra grated Colby cheese, the ciabatta crumbs and rosemary.
- Grill for 4-5 minutes until golden and bubbling.