Two goals in the space of 70 first-half seconds decided this encounter in favour of Laois, earning the midlanders their first All-Ireland junior title.
The final margin was very hard on a Roscommon team that contributed plenty to the game but just lacked a clinical edge in attack.
The Connacht representatives lost by 13 points when the sides met in the group stages, but there was nothing one-sided about this affair, despite the final margin.
The teams were locked on 0-3 each when Laois - led by team captain Niamh Dollard - made the definitive move at the end of the first quarter.
Sarah Ann Fitzgerald toe-poked to the net after her penalty was initally saved by Roscommon goalkeeper Caroline Connaughton, and a minute later Laura Marie Maher finished clinically after killing the sliotar brilliantly with her hurley.
That kept Laois in front even as they endured significant bouts of pressure from the westerners.
Annette McGeeney struck a good point, but four wides prevented Roscommon from making further inroads.
Instead, despite playing second fiddle for most of the second quarter, Laois finished with three points, including a wonderful Elaine Mahony strike from 60 metres, to lead at the interval by 2-6 to 0-4.
Roscommon were on top early in the latter period too, and a well-taken goal two minutes after the resumption from Niamh Farrell, followed by a pointed Kelley Hopkins free, got them back into the game.
However, they could not capitalise on the good work of midfielder Rachel Fitzmaurice and half-back Susan Spillane, and paid the price as player of the match Louise Mahony showed how it was done.
The Harps' sharpshooter raised the siege with a fine point from play. She kept the scoreboard ticking over with five further scores to bring her tally to nine and end Laois' run of two losing final appearances in memorable fashion.
Player of the Match: Louise Mahony (Laois)
Scorers - Laois: L Mahony 0-9 (7fs); SA Fitzgerald, LM Maher 1-0 each; E Mahony, N Dollard, A Burke 0-1 each.
Roscommon: K Hopkins 0-4 (3fs, 1 '45); N Farrell 1-0; A McGeeney, C Curley 0-1 each.
Laois - L Dunne; M Burke, R Bermingham, A Burke; E Mahony, E Delaney, S Creagh; O Parkinson, SA Fitzgerald; N Dollard, L Mahony, A O'Dea; A Burke, LM Maher, A Loughman. Subs: D Mortimer for O'Dea (21), C Walsh for Creagh (60), S Moylan for Burke (60).
Roscommon - C Connaughton; C Killeen, S Coyle, A Byrne; S Spillane, E Daly, J Beattie; N Coyle, R Fitzmaurice; K Hopkins, A McGeeney, R Brennan; C Curley, N Farrell, F Connell-Jones. Subs: M Fannon for Connell-Jones (22), C Dowling for Brennan (42), M Brennan for Curley (57), N McCormack for Farrell (60), C Morris for Killeen (60).
Ref - G Coulter (Down)