For a roasted Garlic Salad Dressing (refrigerated) I take a 5 pound jar of peeled garlic (available thru your local produce section, or in 1# jars at Costco) put it in a roasting pan with some olive oil and roast it in the oven (325F-ish) until nice and nutty brown. Stir every so often to keep the cloves coated in oil and so the ones on the edges don't get burned.
When sufficiently roasted, drain the olive oil, to be used in the salad dressing, and blitz the cloves in the food processor until a thick smooth-ish paste. This paste can be frozen in smaller containers (or do the ice cube tray trick) for later use.
It can also be frozen in flat ziplock freezer bags which is convenient for home use. Just break off a chunk and return it to the freezer. I do the same thing with fresh garlic. FP a large quantity and freezer bag it. Break off pieces as needed.
I think you may need to just add more garlic/onion if the flavor isn't coming thru. obviously, garlic powder aint the same at all to roasted garlic.
When making sauces that contain oil, use a lot of caution. Pasta sauces are processed in jars with metal lids using pressure canning. Hummus is refrigerated. Other salad dressings are refrigerated, or they are mfg in facilities with way better equipment than a home kitchen.
I have not experimented with dry roasting onions or garlic. Don't know how that would work, I'm thinking it wouldn't get that deep rich flavor. Maybe at this point, play around with the sauce and ingredients using oil and keep it refrigerated, or pressure can in small jars. 8z jam jars are readily available. If you want to go fancier, There are lots of different options that use metal lids that can be pressure canned. Contact the seller directly to make sure the caps on the woozy bottles are appropriate for pressure canning.
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EDIT- I have not tried it, but there is roasted garlic powder...
Garlic is technically a lily and a member of the onion family, and though its white flowers are lovely the tasty bulb is what we care about. Its sweet, savory, sulfur-y flavor is intoxicating. To make this roasted garlic powder spice we take bulbs of garlic and slowly roast them until deeply...
www.spicejungle.com
Reading their description, they do not mention using oil, which, if they did, it would have to be listed in the product description. I'd get a couple pounds of fresh peeled garlic and just try it!. SS or glass/Corning roasting pan, no aluminum or cast iron. When blitzing, use one of the liquids of your hot sauce. It will need some kind of liquid to move around in the food processor.
Also, If you get the 5# jar from your local grocer or food service Cash-n-Carry type store, you can also freeze extra cloves as is. Roast some, grind some, freeze some....
Hope this helps, keep us posted and Have Fun!
SL