A roaster oven is very much like a conventional oven, only smaller, moister, and quite possibly, not able to generate (or hold) the highest heat. Used properly, and in good working order, it can cook foods as safely as a regular oven.

It will not be a challenge for you to get that broth to a simmer in the roaster oven, at which point it and the turkey will certainly be at safe eating temperatures. What you don't want to do is have your leftovers lingering for more than a couple of hours in what the US Department of Agriculture considers the "danger zone," 40°F to 140°F (5°C to 60°C). Keep them below that range in a refrigerator or get them above it in an oven or roaster oven, and don't let them spend much time in between.

Any roaster oven worth its salt – which is certainly capable of cooking a turkey – can reheat leftovers. As with the roasting process, you don't want to let out heat by opening the lid again and again. A roaster oven essentially steams your food, so using it to heat broth is ideal. There is a danger of overheating and drying out your turkey, but heating it in broth in a roaster oven is as safe a way as possible to prevent this. We would keep the leftovers from getting much above 150°F/160°F (65°C/71°C), which is absolutely not the same thing as setting the roaster oven to 150°F/160°F. We trust you will use your probe thermometer to know when the leftovers are ready.