The third set of Innistrad, code-named “Roll”, is now revealed as Avacyn Restored. This announcement was made at the mothership last Thursday, stating that this expansion will be a large set and considered separate when drafted. Quoting from the announcement page,

This means that Innistrad Block Constructed will be composed of all three sets, but Avacyn Restored will be drafted by itself. Sealed events will use six Avacyn Restored booster packs.

Here are the additional info of the set:

Set Name: Avacyn Restored

Block: Set 3 of 3 in the Innistrad block

Number of Cards: 244

Prerelease Events: April 28-29, 2012

Release Date: May 4, 2012

Launch Weekend: May 4-6, 2012

Game Day: May 25-26, 2012

Pro Tour Avacyn Restored Dates: May 11-13, 2012

Pro Tour Avacyn Restored Location: Barcelona, Spain

Pro Tour Avacyn Restored Formats:
Swiss:
Innistrad Block Constructed
Avacyn Restored Draft
Top 8:
Innistrad Block Constructed

Official Three-Letter Code: AVR

Twitter Hashtag: #MTGAVR

Design Team:
Brian Tinsman (lead)
Mark L. Gottlieb
Dave Guskin
Kenneth Nagle
Bill Rose
Mark Rosewater

Development Team:
David Humpherys (lead)
Mark Globus
Dave Guskin
Erik Lauer
Billy Moreno
Matt Sernett

And here is the set’s expansion symbol: