I did that last year and again this year... roasted tomatoes, peppers, onions, garlic, turned into
sauce and canned it.
I get so many tomatoes from the farm I belong to that I can't keep up. So last year I sliced them, put them on a baking sheet drizzled with olive oil, tossed in some quartered onions, whole peeled garlic and stems of fresh oregano and thyme. Once they were shriveled, I put them in plastic containers and threw in the freezer. I deglazed the pan with water (or wine if it was available) and tossed that in the freezer too. I also roasted sweet red, yellow, orange and green peppers, seeded and skinned - again tossing them in containers and then in the freezer.
Soon I was at the point that nothing else would fit in the freezer - so I decided to can them. I tossed all in a large pot cooked it slow and the whizzed with a stick blender. Looking at canning recipes I knew I had to add some acid - so I bought citric acid (didn't want to add vinegar or lemon flavor). Ended up with a realllly thick sauce. The most AWESOME sauce I've ever had.
I'm just finishing up last year's sauce.... And this year the same is happening... freezer filled with containers of roasted veggies and a whole huge basket of tomatoes sitting on the counter ripening. Later this week I'll be roasting them. Once the farm stops with the tomatoes I'll make sauce.