It would be so much work(and money if you think about the feed to grow out all the ones with the traits you want) to do that when it is easier just to buy good ones from the start.
You might want to check over the sticky at the top of the page for the differences. Its Araucana who are rumpless, not Ameraucana but Amers do have the beards and muffs. So, no, you unless you have rumpless EE hens you arent going to get them with purebred Amer Roos. You will have a nice flock of EE's though.
If you want Ameraucana that meet the Standard you are better off buying eggs from someone on BYC or birds/eggs/chicks from someone in the Ameraucana Breeders Club. Or even buy some chicks from the breeder who you are getting these Roos from. But be clear.the odds are these Roos will throw some bearded chicks and some not with a purebred hen. Again great if youhave a flock of EE's, not so if you want to breed Ameraucanas that meet the Standard. These Roos are culls from a breeding program, just keep that in mind and what you do depends on what you want your end result to be.
You would probably have alot of fun breeding yours with these, but you would have to produce so many chicks to get a visual standard....and even if it looks purebred, it just isnt going to reproduce pure for you. Not a problem if its just your project, but you would never be able to sell them as purebred Ameraucanas. I think the Roos are a good example for you to learn...even a good breeder gets traits that are undesirable now and again. You just dont use them for breeding if you want purebreds that meet a Standard. BUT backyard flocks...just fine!!
