Ok, Amiga fans, we're going to have to do a little bit more work to get things working...http://www.ultimateamiga.co.uk/HostedPr ... oPieAmiga/
This is what I used. The guide is very *very* comprehensive, and includes video tutorials so I won't try and go over it again here, but I will summarise what it achieves. After you've run through the tutorial, you will be able to run WHDLoad version of an amiga game straight from the Retropie menus, as seen at the Cottage. A WHDLoad version combines multiple disk games into a single file so that you don't have to concern yourself with swapping disk images. The community has been doing this for a *long* time, so basically every game ever released commercially on the Amiga should have WHDLoad version available.
YOU WILL NEED a kickstart ROM or two. The best, cheapest, legal way to do this is to buy Amiga Forever Essentials
for £1.79 on the Google App store and copy the Kickstart ROMs out of that. There are of course other ways to get them (But don't PM me asking for them, obv. That's illegal, you pirate).
You will also need games. If you only want a few specific games, then http://WHDload.com
(EDIT: My bad, it's http://whdownload.com/
)is what you want. The tutorial listed above tell you what to do with the files. There are of course packs available to download. These are usually split into ECS (original amiga games), AGA (A1200 games), CD32 (Er... CD32 games) and demos (Fuck yeah, Jesus on E!).
whdload packs here http://kg.whdownload.com/kgwhd
I personally just had the ECS pack, as in my youth I only ever had an A500+ so those were the games I wanted to play. But you do you and get whatever you want. You want Superfrog? You can have it. You want Deluxe Galaga? It's there! You want Alien Fish Finger? Get away from me, you freak.
Anyway! Hope this has been useful. I'm available for questions and stuff. Like and subscribe for more! http://kg.whdownload.com/kgwhd