I just use chopped tomatoes...or passata if you don't want the lumps and add a teaspoon of sweetener and salt and pepper. Shop bought sauces tend to have added fat and cream but if you want the syn value for a specific one I'm sure i can help
Like Tazzy & Rainbow - I also use Passata - I buy the herbs/oinion variety and if I want it to be a bit more chunky - I add mushrooms, courgette or oinions!
My leader mentioned her one last night roast vegetables with frylight garlic onions mushrooms courgettes etc put them in blender with passata and you have a sauce, sounds easy I may give it a go