Preheat oven to 200 C or 400 F.
To make the honey mustard sauce, place honey, mustard and red chili flakes in a small bowl. Stir to combine.
Place potatoes, red onions and carrots in a large bowl. Add honey mustard sauce and vegetable oil. Toss. Season with salt and pepper.
Arrange potatoes, onions and carrots in a shallow baking tray. Add garlic and rosemary. Bake for about 20 minutes or until the potatoes are tender.
Meanwhile, heat a frying pan over high heat. Add sausages. Cook, turning, for about 4 minutes or until the sausages are brown all over.
Transfer sausages to the baking tray. Add cherry tomatoes.
Bake for a further 10 minutes or until the sausages are cooked through and tomatoes begin to collapse.