One of my favorite “convenience” foods in progress:
Every summer and fall, I chop up tons of peppers, tomatoes, summer squash, and eggplant in bite-sized pieces and roast them in a baking dish ’til done. Sometimes I add a little basil or rosemary, sometimes just the usual salt, pepper, and a drizzling of olive oil.
If I don’t have one of the ingredients (I don’t have eggplant yet), that’s fine too. The basis is really the peppers and tomatoes anyhow. You can also add a little onion or garlic, but just a little–those flavors get stronger in the freezer. Okra works, and snap beans do too.
Cauliflower or broccoli are not good bets because their flavors can overwhelm and get skunky. I don’t add potatoes because I usually use the mix with a starch-based recipe. If for some reason you don’t have tomatoes (oh! the horror!), a mix of just roasted peppers and summer squash is nice, too.
I pack the portioned-out roasted-then-cooled veggies in freezer bags or boxes and use them throughout the winter in pasta sauces, on homemade pizza, in soup, etc. I usually put about two cups in each bag and label if there’s anything non-standard (“with rosemary,” or “spicy!” if I used a lot of hot peppers).