If you are comparing it to a gas oven, then yes, it does not heat up the kitchen like using a gas oven, but it can heat up a kitchen more than a well-insulated electric oven, depending on the task being done. This is not meant as a knock against the roaster oven, just a cautionary statement about using one during the summer when any additional heat source is best kept out of the living area. Oven meals were generally reduced during the summer in the years before air conditioning. People in the south often used these roaster ovens on porches during the summer when they had gas ranges in their kitchens as did our former neighbors when they lived in an apartment. At that time, their old apartment model gas range did not have an oven thermostat so the thermostatic control of the roaster oven was a real boon to precise oven cooking.
I will share one bit of hard-earned knowledge. If you are baking in a Bundt Pan in a roaster oven, you need to place a trivet like one from a 4 or 6 quart pressure cooker on the load and lift rack before placing the Bundt Pan in the oven. While the load and lift rack is adequate to keep flat bottom cake and pie pans from coming in direct contact with the bottom on the oven, the fluted outside of the Bundt Pan needs the greater surface area of the additional trivet to provide a cushion of air between the oven bottom and the pan. The Westinghouse Roaster Oven bakes beautiful pound cakes that are beautifully browned on all sides. Once, when the bake element in mom's oven went out just as she was going to bake a pan of brownies, she fired up the RO and reported excellent results.