Jamie Clarke had been outstanding, and a succession of markers were unable to stem his influence as he blasted 1-3 from play and Armagh built up a double scores lead by the interval.
There was no wind and the Ulstermen were well worth their 1-7 to 0-5 half-time advantage. It was hard to see how anything was going to change after the restart.
A simple return to tradition changed it all. Armagh had thrived on a two-man full-forward line. Full-forward Caolan Rafferty had spent the day out the field and Clarke and Gavin McParland revelled in the open space inside. It is impossible to man-mark in such circumstances.
Instead, Roscommon just filled the space with their six backs and let those out the field deal with the extra man. Cathal Cregg led from the front in winning hard ball and Karol Mannion, Cathal Shine and Michael Finneran, when he came on, also won the collisions.
Clarke was smothered in the Armagh attack and they didn’t have a Plan B. They went 26 minutes of the second half without scoring, Clarke’s only shot at the posts was a free which went wide and it was sub Tony Kernan who got their only two points of the second period.
It was all so different earlier. Armagh had an edge in the physical exchanges and were not shy in showing it. Roscommon looked like a group of players who felt they had better ways to while away the summer.
Roscommon failed to score from play in the opening half and most of their five wides were woeful efforts, the sort of tired kicks a player would try at the end of training.
Armagh will regret not making more of their dominance but Clarke’s fine goal after eight minutes and a lead of five points at the interval seemed more than sufficient.
Roscommon had other ideas. Donie Shine put Senan Kilbride in for a rocket of a goal inside 30 seconds. The place erupted. Suddenly, there was a pep to their step, they started to win the hard challenges and got more than a rub of the green from referee Maurice Deegan in the 50-50 calls.
Roscommon’s rise was in direct proportion to Armagh’s descent. They pumped hopeful ball into attack but found defenders Seanie McDermott, Peter Domican and Sean Purcell there to drive it back out.
Roscommon used possession well as their play became infused with confidence. It was hard to believe it was the same side who looked so disinterested and inferior in the opening half. They followed up the goal with a point from Cathal Shine from 30 metres and then Donie Shine levelled after 44 minutes.
Donie Shine pushed Roscommon into a lead they never surrendered after Armagh goalkeeper Phillip McEvoy was penalised for holding on to the ball too long after 49 minutes.
Roscommon hit eight second half wides but Donie Shine and Karol Mannion found the range to open up a lead of 1-10 to 0-7 after 60 minutes.
Armagh finally ended 26 barren minutes in the second half when sub Tony Kernan pointed from the left with nine minutes left. But while Cregg hit back for Roscommon a nervous finish was guaranteed when Kernan pointed a free.
A smash and grab job would have been cruel luck on the Rossies at that stage but it never looked like materialising.
It’s always worth staying around till the end, and you just suspect this win will have done as much for Roscommon than all the underage success they have enjoyed in the past few years.
Scorers for Roscommon: D Shine 0-7 (6fs), S Kilbride 1-1 (1f), C Cregg, K Mannion, C Shine 0-1 each.
Scorers for Armagh: J Clarke 1-3, A Forker 0-2fs, T Kernan 0-2 (1f), J Hanratty, A Duffy 0-1 each.
Subs for Roscommon: G Heneghan for Kilroy (35), M Finneran for C Shine (43), D Ward for Collins (55), D McDermott for Compton (62), J Rogers for Cregg (67).
Subs for Armagh: M Mackin for Forker (43), C Vernon for McParland (55), J Lavery for McKenna (60), T Kernan for Dyas (60), J Kingham for Duffy (65).
Referee: Maurice Deegan (Laois).