Deadline for Contract Extensions?

[*ochocincos*]

Is there a team/league deadline for players to sign extensions before the first game of the season or have to wait until after the season is over?

I seem to recall there being big pressure for Geno Atkins to sign an extension before the season started in 2013, in which he signed Sept 3.
AJ Green signed his extension on Sept 11, 2015. The first game of the season was Sept 13.

The reason I ask is because the Bengals typically try to sign their players to extensions before the season starts and extensions don't happen in the middle of the season.

Specifically, here's an excerpt from Jim Owczarski about Green's extension...

Jim O. Wrote:After nearly reaching a deal on Thursday afternoon, The Enquirer has learned the Cincinnati Bengals and star wide receiver A.J. Green have come to terms on a long-term contract extension, just an hour before the club's deadline to get the contract worked out and the team took off for Oakland.

http://www.cincinnati.com/story/sports/nfl/bengals/2016/03/04/cincinnati-bengals-aj-green-contract-extension/71643144/

This makes me wonder if this means players like Burfict and Eifert won't in fact get contract extensions done this year and instead see what happens after the season?
Also, does that mean the team will "roll-over" their approximate $17 mill in cap space to next year?