Biermann tore his right Achilles tendon and Ewing separated his left shoulder in Sunday's 31-24 win over the St. Louis Rams. Coach Mike Smith said Monday each will be placed on injured reserve.
"As I say many times, one man's misfortune is another man's opportunity, and we've got some guys that we expect are going to step up and make some plays for us," Smith said.
The loss of Biermann will lead to expanded roles for defensive ends Jonathan Massaquoi and rookie Malliciah Goodman. The versatile Biermann also played a linebacker position which had him dropping back in pass coverage.
"There's a role for a [backup] defensive end when Kroy was playing defensive end and there's a role for one of the [backup] linebackers," Smith said. "We've put that in place from the very beginning.
"As you know, your roster never stays the same from year to year and usually it doesn't stay the same from week to week. We will make the adjustments and move forward."
Biermann was credited with two tackles before leaving the field on a cart late in the first half.
Biermann, a fifth-round pick in 2008, has 16½ career sacks, including four in 2012. Osi Umenyiora, an offseason free-agent signee, is the team's other starting defensive end.
Ewing's injury will lead to more playing time for Jason Snelling, who ran for a touchdown against the Rams after starting running back Steven Jackson left the game with a thigh injury. Snelling has played fullback and running back in his seven seasons with the Falcons.
"Jason has always stepped up whenever he's had an opportunity," Smith said. "I thought he did an outstanding job yesterday."
Ewing did not have a carry but had one catch for 14 yards before hurting his shoulder in the first quarter.
This is the second straight year Ewing has suffered a season-ending injury. His tore the anterior cruciate ligament in his right knee before his 2012 rookie season.
Smith said he met with Ewing on Monday morning.
"It's tough because he's not been able to stay on the field," Smith said. "He's had the knee injury last year and it ended with him going on reserve injured early. The same thing is happening this year.
"As I told him hey, we've just got to get you healthy. March and April will roll around and we'll reconnect and get moving forward."
The Falcons beat the Rams despite losing five starters to injury: Biermann, Ewing, Jackson, linebacker Sean Weatherspoon (foot) and cornerback Asante Samuel (thigh). Samuel missed the opening game at New Orleans with a thigh injury.
Backup defensive end Cliff Matthews returned after leaving with a neck injury.
The Falcons had other injury concerns entering the game. Receiver Roddy White has been slowed by an ankle sprain since the third week of the preseason. His playing time has been limited in the first two regular-season games.
Smith, who normally gives injury updates on Wednesdays unless a player suffers a season-ending injury, had no updates Monday on Jackson, Weatherspoon or Samuel.
The Falcons play at Miami next Sunday.