That's what I use for my mirpoix. I actually got pre-chopped mirpoix from Trader Joe's. I cook my roast with it then I use an immersion blender and make a gravy from it. Turn the pot back onto saute and boil it down. You can splash some wine or sherry into it if you want. Makes a nice gravy.

Once you open the vent though it lets all that smell out into the house! I sometimes cook things in the garage for that reason. Just put it on my workbench and plug it in.