ACFT 7 MI IN TRAIL OF B757; SAME ALT; EXPERIENCED WAKE TURB AND RAPID ROLL FROM A 20 DEG BANK TO 45 DEG BANK. ACFT IN COMPLETE CTL AND INSTANTLY RETURNED TO NORMAL FLT.

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I WAS FO; PF. WE WERE RECEIVING RADAR VECTORS AFTER PASSING KAINS INTXN TO MIA. A VISUAL APCH EXPECTED TO RWY 12. LCL WX APPROX 3000 FT SCATTERED; 75 DEGS F; WINDS 120 DEGS 18 KTS WITH LLWS RPTS. AT 8000 FT I WAS HAND FLYING IN VMC. AN ACFT WAS OBSERVED ON TCASII AND THEN VISUALLY TO BE APPROX 7-8 MI AT 8000 FT MSL. WE WERE ON ARR AT KAINS AND GIVEN HEADING 270 DEGS. IN THE TURN WE ENCOUNTERED MODERATE TURB WITH SLIGHT ALT FLUCTUATIONS AND RAPID ROLL FROM A 20 DEG BANK TURN TO APPROX 45 DEGS. CTL WAS NEVER LOST; TURN WAS COMPLETED. CAPT ASKED MIA APCH WHAT TYPE ACFT WE WERE FOLLOWING AND THE CTLR ADVISED A B757. WE ADVISED HIM OF WAKE TURB ENCOUNTER. CTLR SAID WE WERE 7 MI IN TRAIL. WE THEN RECEIVED DELAYING VECTORS FOR ADDITIONAL SPACING AS ACFT WAS CONDUCTING ILS TO RWY 09L. FLT CONTINUED WITHOUT FURTHER INCIDENT. DURING DEPLANING; A PAX COMMENTED ABOUT THE 'BIG BUMP.' EVEN THOUGH I HAVE FOLLOWED MANY B757'S ON APCH WITHOUT INCIDENT I FEEL CTLRS SHOULD NOTIFY ACFT THAT ARE WITHIN 10 MI IN TRAIL OF ALL B757'S. IT IS OBVIOUS THE B757 HAS A WAKE TURB PROB. I AM CURIOUS THAT NOT MUCH NEWS HAS COME FROM BOEING ON POSSIBLE REMEDIES TO ELIMINATE THE PROB (AS MUCH AS FEASIBLE). RETROFIT MAY NOT BE FINANCIALLY AN OPTION BUT I HOPE SOME RESEARCH IS BEING CONDUCTED. WHEN MADE AWARE I AM FOLLOWING A B757 I WILL CONTINUE TO STAY UPWIND; ABOVE GS AND LAND LONG WHEN AT ALL POSSIBLE BUT I NEED TO KNOW HE'S THERE WITHOUT HIS WAKE TURB BEING THE ONLY CALLING CARD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: CALLBACK IN CONJUNCTION WITH WAKE TURB SPECIAL STUDY. RPTR FLC WAS SURPRISED AT THE RATE OF ROLL FROM 20 DEG BANK TO INSTANTLY 45 DEG BANK DUE TO PRECEDING B757. FLC HAD ACFT BOTH VISUALLY AND ON TCASII; BUT DIDN'T KNOW IT WAS A B757. WHEN ATC WAS QUESTIONED ABOUT THE PRECEDING ACFT TYPE; THE CTLR WAS SURPRISED THAT THEY HAD EXPERIENCED THE WAKE TURB BECAUSE RPTR WAS 7 MI IN TRAIL OF THE B757. APCH CTL THEN PROVIDED GREATER SPACING FOR RPTR WITH RADAR VECTORS. BESIDES THE INSTANT BANK INCREASE; NO FURTHER CTL PROBS OCCURRED. SEVERAL PAX MADE COMMENTS WHEN DEPLANING ABOUT THE 'BIG BUMP.'