Hi drforbis -
By roaster oven, do you mean one of the 18-quart sized plug-into-the-wall types? If so, no need - treat it just like you would an oven, rather than a crockpot.
I've made turkey in mine (with great results) many times, large meat roasts, and even make desserts like brownies.
Welcome to DC - and don't worry if you get many replies today - most members are here during the week, rather than weekends)