Roscommon completed their hat-trick of victories over Mayo at this level with a blistering second-half display in Kiltoom.
Donal Smith's 54th-minute goal proved to be the game's defining score, but some wayward shooting by the home side kept Mayo in the hunt.
Mayo's dominance of the second quarter gave them a slight edge at the break, 0-8 to 0-7. But there was only one team in it in the second half as a fresher Roscommon side, inspired by the introduction of Scott Oates, John McManus and Cathal Shine, took over completely.
A 50th-minute free from the cultured left boot of Smith gave them the lead.
Then the Boyle player gathered Ciaran Murtagh's high delivery, and blasted home. Roscommon now meet Sligo or Leitrim in the final.
SCORERS - Roscommon: D Smith 1-4 (3f), N Kilroy, C Compton, C Connolly, N Daly, F Cregg, S Oates, C Murtagh 0-1 each. Mayo: C O'Connor (3f), C O'Shea 0-3 each, E Regan (1f) 0-2, J Shaughnessy (1f), A Walsh ('45) 0-1 each.
ROSCOMMON -- N Connaughton; R Stack, C Duignan, D Murray; C Daly, P Brogan, C Cafferky; F Kelly, N Daly; F Cregg, N Kilroy, D Clabby; C Connolly, C Compton, D Smith. Subs: S Oates for Clabby (h-t), J McManus for Connolly (41), C Shine for Kelly (41), C Murtagh for Cregg (50).
MAYO -- P Mannion; M Walsh, N Freeman, D Gavin; C Crowe, S McDermott, M Forde; A Walsh, D Geraghty; A Farrell, C O'Connor, B Harrison; E Regan, D Coen, C O'Shea. Subs: J Shaughnessy for Harrison (35), D Kirby for Farrell (43), C Walsh for Coen (50), A O'Toole for Regan (57).
REF -- R McBrien (Leitrim).