I have a 13qt villa ware (think magnalite) covered roaster. I bought it at Tuesday Morning for an absurdly low price and thought "when will I ever use this?"
Well, big batches of chili for a group gathering or church supper. It gets used all the time. Works wonderfully both on the range top and in the oven. It is thick polished aluminum, nothing burns.
So yes, such a roaster is very equal to a slow cooker. Also, those electric roaster/ovens ... what do they hold--20 or more qts...excellent as a "huge"slow cooker. Mine is an old Sunbeam and I can do a turkey in one if need be.
Would I walk away, leave the house, go to work etc as I might with a crock pot? I never have but I don't see why I couldn't. It's the same principle, etc as a crock pot. Keep the temp very low, for sure.