SmilingNage

"But in Kote-gaeshi of this topic, i don't think the rolling version works well. In Irimi-nage, if the nage put his/her leg behind your back the proper way, the rolling version won't work either. In shiho-nage, if the nage put too much down ward pressure and hold your wrist until you're on the ground, the rolling version won't do well either. In koshi-nage and juji-nage, you have to be good and nage allow you to roll out."

Not for nothing, but if you get trapped from doing a roll, either forward or back, during a throw, its either an exceptional Nage or bad ukemi. I lean towards bad ukemi.
Uke really needs to protect himself during the course of a throw. You cant always rely on nage to watch out for you. In fact, you shouldn't rely on anyone but your own ukemi. Ukemi is self reliance and about self preservation. High/Break falls require alot of trust between Nage and Uke. The great teachers will often put you in a situation where you have to take the high fall, but their control is such for the most part your high fall will be safe as their lead directs how and where you will fall. Nage should throw in responsible safe manner,but Uke needs to be in control as well.
That being said You can pretty much take back rolls for shiho-nage,irimi-nage,,juji-nage, pretty much any projection regardless of the speed at which you are working.The high fall from shiho-nage is a forward roll in nature. The fall mechanics are similar except you don't have the benefit of putting your arm on the mat to do a roll with. Most high falls from koshinage are merely rolls around or over Nage. Kote Gaeshi is one the easier throws to learn how to take high falls from. As Nage can change the height of fall by adjusting how high he holds and releases Nage arm. Low release points make it easier for learning Ukes to roll over their wrists. The higher the release point is higher the tougher it becomes to do the high fall. As Uke must leap higher to get over their wrist.

"In the ikyo, nikyo and sankyo, how do you rollout? You need front breakfall to save your face, literally."

Its been my experience, that rolling out of these techniques is a means to escape or leads to Henka waza(reversals). Also while those techniques can be used a projection( which can be rolled out of) for the most part they lead to pins. Good ukemi, which in this case experience and body movement, prevent face planting by using the uncaptured arm to support the body so uke can lower him or herself to the mat.

The teachers who don't teach "breakfall" have robbed their students a simple and effective self-defense method.[/quote]

" A break fall is good ukemi gone bad" not sure who I robbed that line from I think it may have been my sensei. Basically You survived up to a point, but now you are forced to take a break fall, ie all other options have failed, time for the back up plan or my joints/arms will give a new meaning to the phrase double jointed. Break falls are great to know, as they give you more options,survivability, but good fundamental forward and back rolls ukemi for the most part will get you through most ukemi situations.
Break falls aren't simple, in fact not a very natural response. Just think if they were so simple almost no one would be injured if they fell or tripped. If simplicity could be associated with break falls, Then the world would look like it had been taken over Chinese acrobats and everyone could preform high falls on command and never be injured. Could you imagine walking downtown in NYC where everyone would take break falls instead of falling/tripping? It would be a insurance company's nightmare or dream( a world where no ever slipped or fell, a world with a bunch leaping daredevils. ) AIG beware as the aiki community releases a torrent of break falling pedestrians onto your streets.
Not every dojo is equipped with mat that can support high fall training. Not every student can take high falls. Not many students reach a level of proficiency or talent to learn break falls and the list goes on. So there are alot of circumstances , safety of practice being the utmost concern, for not teaching high fall.
Aikido is silent art, in that most of the learning comes from training. Actual hands on practice(lots of it) is the best way to get a point through. So I would differ to your teacher and sempai to show you the way, especially in matters of ukemi. You may pick up some good advice through conversation, but it is through practice that lessons will be learned and truths brought out.
That been my experience so far(though I haven't come across a city whose citizenry has been trained by Chinese acrobats) maybe yours are different.