We have yet to see a roaster manufacturer allow anyone to use a roasting bag inside their appliances. You are to keep your roaster bag from touching the heating element or sides or top of a standard oven, in case they touch a hot spot and melt. There is essentially no way for an oven bag not to touch major portions of the sides and lid of a roaster oven.
To be more specific, one bag manufacturer says its bags "should not be used:
- under a broiler
- on the stovetop
- on barbecue grills
- in toaster ovens
- in countertop convection ovens
- in electric roaster ovens
- or as boiling bags."
So there.
stated elsewhere at Ochef, you can give a roaster-oven turkey the color of brown, but probably not the flavor of brown.