You treat them just as you would fresh tomatoes. They will just be softer is all. Do you want a smooth sauce or a chunky sauce? And you have the food mill which is what most use.

If you want a smooth sauce then all you have to do is thaw, run them through the mill to remove the skins and seeds, then cook the sauce down to the desired consistency. You can still roast them first if you wish before milling. Why do you feel they can't still be roasted? The fact that they were frozen doesn't mean you can't roast them still.

If you want a chunky sauce then it is just a matter of chopping them or using a blender or food processor. Some remove the skins, some don't. It's your choice. Then cook the sauce to the desired consistency. No reason they can't be roasted first too.

Dave

I was thinking that the defrosted tomatoes would be too soft and mooshy to roast. Do you roast them while they are frozen, or defrost them first? I would really like to roast them!

You can do it either way but it would take a lot longer in the oven and use a lot more electricity if you put them in the oven frozen. I thaw them first, drain them a little, then spread them all out on pans/cookie sheets and stick them in the oven.

Dave