Fairly Common
Roasters of old were made by Westinghouse and Nesco amoung others. Modern units can by had by such brands as Rival, Nesco and several others.
Vintage roasters were VERY popular in the day when families either didn't have a second (summer) kitchen, thus Madame could prepare meals without heating up her kitchen in warm weather (a great deal in the days before air conditioning), and or provided a way to handle overflow cooking during holidays. Units could also be taken to cabins and indeed camping/picnics, long as there was source of electric power. Oh and units were great for "slow" cooking as the first sort of "crock pot".
Being as all the above may, vintage roasters like the Westinghouse were horrible energy hogs, (plug one into a Kill-O-Watt, or simply go to one's meter and watch the dials zoom round and round), they also weren't very well insulated. While cooler than using an oven of the day, vintage roasters had to cycle often to hold their heat, and could get quite warm.
One could purchase all sorts of attachments for Westinghouse roasters. Grills, broilers and so forth allowed Madame to make all sorts of dishes. Have an owner's manual/recipe book some where for a Westinghouse roaster long since moved on.
Many persons like roasters then and today for doing large roasts or birds such as turkey, as well as dishes for a crowd. Then inner lining comes out so one can either take the dish on the go (pot lucks, church suppers, etc) or right to the table. In any case again one still leaves the main oven free for other things.