This is the Rosty Beast Druid Deck NA Summer Prelims he used. A lot of people have been asking what his list was and I tracked it down to share here. Beast Druid lists are going to change when the new card Menagerie Warden comes out tonight.
I think Beast Druid decks will be more midrange than this kind of aggressive list when the new card is out, but this was a fun deck to watch Rosty play in the Prelims.
Mulligan Guide for Beast Druid
The perfect start is to curve out with beasts. So Enchanted Raven, into either Huge Toad or Darnassus Aspirant for some ramp depending on what your opponent is doing. Mark of Y’Shaarj is worth keeping if you have a 1-2 drop beast too.