Is this a "roaster oven" or a "toaster oven?" Does it have a front door that hinges down, and a rack or racks inside, with heating elements top and bottom? I'll assume that's it. Some people say to cook the stuffing separately for safety reasons, but I think most people still stuff turkey...just take the stuffing out when it has cooled, and refrigerate it separately from the bird. I'm thinking you cook turkey at 325 degrees for 15 minutes per pound...20 lbs is a big bird! Whatever you would do in an oven, you can do in a toaster oven, and I don't think you would have to adjust cooking times much. I never use water in the pan for turkey, but I cover it loosely with foil (don't leave the edges out of the pan or it'll drip all over). during the last 30 or 45 minutes, take off the foil so the skin can brown nicely.
Did you get a rotisserie attachment with your roaster? These are great for chicken. The one drawback with toaster ovens is that they can be messy to clean. I use min mostly in the summer, I set it outside on the patio so that I can have roast chicken, baked potatoes, casseroles, etc. without heating up the house.

I have an older roaster similar to the one weezie has, and I have roasted a turkey in mine many times. I do like to place foil around mine, to make cleaning the removable pan easier, and it also keeps the turkey from drying out, and basting juices closer to the turkey for flavor. I have fully stuffed my turkey with no problems. The only problem with the one I have is that my turkey will not brown, so when it is done I pop it into the oven long enough to brown it good...But it is a big help having the roaster, as it frees up your oven for other dishes, pies, rolls etc that you want to fix. I have also used mine to sterilize canning jars...I just added boiling water to the roaster set on lower setting and then I could add and remove jars as need.

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