B737-900
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Situational Awareness; Communication Breakdown
ATC Issue All Types; Inflight Event / Encounter Wake Vortex Encounter
Flight Crew Took Evasive Action
Procedure; Environment - Non Weather Related
Wake turbulence encounter at FL350 7 miles in trail of Boeing 757 at same altitude that resulted in roll up to 15 degrees to left and autopilot disengagement and ROLL AUTHORITY; ROLL AUTHORITY announcement. We were behind [the B757] on the GLAVN2 arrival to ATL with a direct 30 kt tailwind.  We were not informed of type of aircraft we were following and had no reason to suspect wake turbulence would be an issue.  We recovered from unexpected roll by rolling wings level and increased in trail separation; followed by descent clearance to clear the 757 wake.  No injuries or complaints from passengers or cabin crew.  We were not made aware of type aircraft we were following; but asked immediately after the event. Advise 737 aircraft when they are in trail of 757.
B737-900 Captain reported encountering wake turbulence at FL350 7 miles in trail of a B757. Reporter stated they were not advised of possible wake.