Barrel Rolls are a cool maneuver. I'd like to communicate something to those that use it as their sole method of dealing with guys on your 6. Are you ready? I have always been able to detect one performing one nearly instantly and move to counter it. In this, I have not been shot down once from someone using this technique on me. Not in years anyway.
On the other side, Barrel Rollers nearly always survive my bounce attempt on them. Kudos to them. 
I notice some are one trick ponies at dealing with being bounced (me included thus this post!). For me it has been a Split-S. Others, like Joker, usually live but I have only seen him use one move to counter me. As I detect him doing his one counter trick I adjust and try to have led waiting at his counter vector. I'm getting better at it. Hint: learn something new dude. ;-)
Greebo too does a Semi Split-S Feign then has led waiting as you miss! BTW that is Jokers move but Greebo is better at it and has more moves.
There are only a few options you have when you are low and slow on the deck after take off. Stick stir, scissors for overshoot and attempt to BRD, or a nose down rudder kick if they are really close. . Other than that, you really are in a tight spot and the enemy plane attacking you should just pull up and come back around. Most people fall right into the trap though.
If you are 3K or higher there a couple of other manuevers, nose down rudder kick with a snap roll usually gets them to miss while saving your E. You can do a nose nose down extended barrel roll to get them to follow, then cut throttle, deply flaps, and roll over them, while they desperatly try to stay on your 6 after gaining more speed following you down. If they are coming straight down on you, pull up into a loop and roll over them. If you think they are going to shoot you in your defensive attempt, roll ailerons right and left, normally makes it hard to shoot.
I fly 109s very well in the defensive and one thing I've learned is that A. Most people are terrible at aiming when you roll your ailerons. B. If you can get them to black out or lead shoot you, nose down and rudder kick in the opposite direction and they won't even know where you went.