Hoover flies an experimental with inverted oil systems among other modifications. It is probably fair to say a aileron roll won't hurt the airframe if done properly. I think a fair argument can be made that rolling/looping aircraft not intended for acrobatics can hurt things attached to the airframe though.
A loop is an entirely different animal than an aileron roll. A loop can get ugly real quick and have massive G loading. Aileron rolls are totally stress free.