Evan Murphy led the way as Galway booked a place in the Connacht MFC final against Mayo on Sunday week after a deserved win in Kiltoom.
Murphy, underage next year and also pursuing a career with Galway United, hit 2-4 to crown a fine display, with full-back Sean Mulkerrin from the Aran Islands also in top form.
Roscommon managed only two points from play during the game, the first of which came at the end of the third quarter. A goal from a penalty from Murphy after five minutes gave Galway a great start and by the interval they were 2-7 to 0-2 ahead.
Murphy was the star performer on show and by half-time had amassed 2-3, with his ability to strike frees from distance off the ground a feature.
Robert Finnerty, a son of former Mayo star Anthony, sent Murphy away for the second goal after 27 minutes before blasting low into the left corner.
Roscommon improved after the break and a goal from a penalty by Brian Derwin gave them hope.
But Barry Goldrick sealed it with Galway's third goal late in the game as the holders advanced to the final in Pearse Stadium on Sunday week.
Scorers - Galway: E Murphy 2-4 (1-0 pen, 1f, 1 '45), B Goldrick 1-1, D Conneely 0-3 (3f), R Finnerty 0-2, S Thornton 0-1. Roscommon: B Derwin 1-1 (1-0 pen), C Lennon 0-3 (2f), L Cregg ('45), J Fetherstone (f), C Heneghan 0-1 each.
Galway - C Haslam; E Deeley, S Mulkerrin, E McFadden; A Quirke, E McDonagh, F Garvey; S Raftery, R Murphy; B Goldrick, E Murphy, R Forde; R Finnerty, F O Laoi, D Conneely. Subs: S Thornton for O Laoi (BC, 19), R Cunningham for Forde (bc, 23), J Gavin for Goldrick (43), Goldrick for Cunningham (48), L Kenny for Deeley (60).
Roscommon - L Cregg; D Duff, A Whyte, S Fallon; P Halpin, A Dowd, L Daly; L Mollahan, C Shanagher; J Fetherstone, C McKeon, K Murphy; D Glynn, C Lennon, M McGloin. Subs: C Heneghan for Glynn (24), N Murray for Mollaghan (31), B Derwin for McKeon (39), C Fahey for Fetherstone (54), F Guihen for Halpin (55).
Ref - E O'Grady (Leitrim)
Connacht MFC semi-final: Mayo 4-11 Leitrim 1-8
A stellar performance by full-forward Ryan O'Donoghue, who scored three of Mayo's four goals, blitzed a hard-working Leitrim side at Pairc Sean MhicDiarmada, Carrick on Shannon.
Mayo got off to a dream start with a goal and a point by O'Donoghue within two minutes and he followed up with his second goal three minutes later to put Leitrim on the back foot. Mayo dominated the first quarter with further scores from Paul Lambert and Colm Moran with Leitrim getting off the mark with a Darragh Rooney free in the ninth minute.
A second Leitrim point by Niall McGovern was followed with Mayo's third goal in the 16th minute but credit to the home side who kept battling and enjoyed the better of the exchanges in the second quarter, resulting in three Rooney pointed frees and a Niall McGovern point from play without reply to leave the half-time score at 3-3 to 0-6 in favour of Mayo.
Two Mayo points on the resumption extended their lead and then in the 39th minute O'Donoghue struck again for his hat-trick to put the game beyond Leitrim. Mayo emptied their bench as Leitrim struggled and in the final ten minutes the visitors hit five points to Leitrim's one before Rooney converted a late penalty.
SCORERS - Leitrim: D Rooney 1-4f, N McGovern 0-2, S Sweeney, J Gilheaney 0-1 each. Mayo: R O'Donoghue 3-4, N McGhee 1-0, O McLaughlin 0-3, P Lambert, C Moran, C Murphy, C Stenson 0-1 each.
LEITRIM - D Maxwell; L Ryan, E Harkin, F Gallogly; C McGloin, J Gilheaney, S Harkin; N McGovern, E Keegan; C Duffy, S Chandler, E Harkin; R O'Rourke, D Rooney, J Glancy. Subs: S Sweeney for J Glancy (27), S McDermott for L Ryan (41), C Kiernan for S Chandler (45), M Dolan for C Duffy (48), A McLoughlin for R O'Rourke (55).
MAYO - A Byrne; C Horan, D Cosgrave, J Cunnane; B O'Malley, M Macken, J Maughan; C Murphy, N Moran; P Lambert, R Egan, O McLaughlin; C Moran, R O'Donoghue, N McGee. Subs: C Stenson for N Moran (35), S Kenny for B O'Malley (45), T Conroy for N McGhee (47), S McGreal for R Egan (55), L Kelly for M Macken (58), E Gibbons for C Moran (60).