Disclamer: by no means I am a baseball expert . This is only my opinion. If it can serve as the starting point of a good discussion, I will be glad. 

Having watched a lot of O's game this year (on TV, of course :)) and witness the debut of several young pitchers and their ups and downs,  I want to give my opinions on what they should work on to make their game better. First and foremost, something positive, it seems that all of them have very good mental makeup, which is essential for success in MLB. Secondly, everyone(maybe minus Berken) has good enough stuff to be successful. They also have flashes of Brilliance(in the case of Bergesen, simply brilliance). It is reasonably to  believe their futures will be great. 

Now comes the suggestions. 

Bergesen: Stamina. That's the only thing I can think of. If he can pitch the way he has been pitched and work up his stamina, he could be a work horse for us for years to come. He has good command and is the most polished rookie we have right now. If he has good stamina, he can work 7+ almost everytime he pitch. 

Hernadez: Command of all his pitches. He has great stuff and is strong. The problem is that he is simply not efficient enough and always get himself into trouble or into fatigue by throwing too many balls. In order for him to be reliable, his command simply has to improve. 

Matusz: Fast ball command and consistency. He is supposed to be a good control guy. It seems that, however, he relies on his off-speed stuff too much. He has a good fast ball, use it! 

Tillman: Fast ball location. Maybe pick up a cut fastball or two simmer or something. His fast ball right now is too straight and if it's not a good location, it would get crushed. I am suprised by his off-speed stuff though. i was under the impression that his breaking ball is not that good. 

Berken: Well, Berken is a good guy. However, he simply has to improve his command and pick up a sinker or something. Right now he has to be very accurate in order to succeed, that simply won't happen. You can't realisticly expect you have all your pitches working everytime you pitch. His future might be in the pen. 

That's all that I can think of right now. Thanks for your time to read the post.