I personally use the big top silicone giant cupcake mold (my dad got it for me for christmas years ago). Its SO easy to remove the chocolate shell with the silicone mold since you can just peel the mold off the shell! The only downside to it is that there is a small horizontal line in the mold to mark where you should fill the batter..but I just turn it to the back, its barely noticeable!
As for recipes I use my normal cake recipes so it just depends on what flavor is wanted. And a good crusting buttercream will help with your sagging rose swirls! Good luck!