I think a lot of it would depend on what you are trying to do. Improve the rolling I would guess.
When I was a youngster, I kept breeding my best rollers to my best rollers and not really keeping track of the blood lines. These birds ended up rolling into the ground and killing themselves. anyway...
If I were to try it, and based on what Jastreb mentioned, I would breed roller to parlour tumbler, then take that offspring (With-out letting it fly, for fear of it killing itself) and breed it back to a roller, then see what happens. Genetics are a great thing to play with, but you have to have some idea of:
1. Where you are
2. Where you want to go
3. What you want to do
4. A way to track your progress
What I have found with most of the people who want to do the cross breeding, in breeding and out breeding, usually start with a good idea, but either do not have the time or resources to stick with it, or get bored or impatient after the first generation. It can be a lot of fun, but if you do decide to go this route, please stick with it, and let us know what your results are (Or at least let me know! I am really interested in this. Who knows, you could end up with AGSG rollers and your name could live on with the pensom and Graham and who know what else.)
Best of luck.
this is a funnie topic;;;
many roller fanciers have done this already;
even i have tried this;;
i'll tell you guys my results.
i bred 6 pairs cause i had big hopes for them.
pair number 1: the babies were blind. they couldent see the sky or anything! at all!
pair number 2: the babies coundent fly higher than 7 feet off the ground. when they get to that hight they will spin like a falling leaf.
pair number 3: had the same results like pair number 2
pair number 4: only one survived, now, this one can acutally fly like a regular bermingham roller, but it started rolling at 3 months, thats was good, had good control, but was taken by a cooper before it hit 5 months. so i never knew the outcome of this boy.
pair number 5: this pair will not fly, at all! they can see, but they cant fly, no, acutally they just dont want to fly, i threw them about 3 months before i gave up on them
all they do is when you throw them, they get to 10 feet, start falling like a leaf.
last pair before i separated the parents, only one survived, this one was blind only one survived, this one was pure junk, will not go higher than 3 feet, flies 3 feet and flips, does that all day,
this was my experience with this cross;
let me tell you guys some thing;;;
DONT WASTE YOUR TIME!