Re: Backward Roll - Risks and benefits
It seems to me that rolling during a stand up engagement is primarily a means of safely extending maai, whether to run away or to re-set the engagement on more favorable terms--as in "select zone 5 and extend" (OK, I know it's really humiliating for an Air Force guy to be quoting a Navy movie, but most folks are unfamiliar with the term in any other context).
Assuming my view is correct, it would seem that it is, therefore, at least useful, if not critical, for martial artists to be able to execute any roll in any direction when the tactical or strategic situation demands an extension. If the opening to extend is to your back and you need to get away, that's the way to go. If you have the time to turn to face the back, do it as a forward roll. If the hole's top the side, go that way.
Of course, any attempt to extend can be followed and exploited by a determined adversary, but ya do what ya can. If you've never trained rolling in a particular direction, though, you've already limited your options in a way that can come back to bite you. If training accidents are your concern, structure training so that the probability of an accident is minimized--one way is to have a general rule to always throw to the outside edge of the mat.