Led by Johnson’s 5-30, the Roos won their first game of the season by eight wickets after eclipsing the Hawks’ 149 in the 43rd over of the one-day contest at Breckler Park.
The world-class paceman took three of Wanneroo’s first four wickets to have the hosts floundering at 4-16.
In a sign of how difficult the batsmen found it to face Johnson’s speed, he bowled all five of his victims with three of them falling for ducks.
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READ NOWJosh Marrs top scored for the Hawks with 34, while Wanneroo’s Mathew Dzodzos, Kyle Millar, Josh Quelch, Matthew Leach and Rob Richards supported Johnson with a wicket each.
Richards impressed with an unbeaten 69 to lead Wanneroo’s chase.
Wanneroo were without Johnson on Sunday when they lost to league leaders Perth by 82 runs at Kingsway in the last of its early-season one-dayers.
The Roos fell for 206, chasing the Demons’ 3-288.
Perth’s Jonathan Wells starred with 125, while Dain Moreton (63) and Adam Wheater (69) each scored half centuries.
Jacob Johnston top scored for the hosts with 49 as former WA seamer Ryan Duffield took 3-14.
Wanneroo’s victory over the weekend lifted it from last place to 15th.
The Roos face Scarborough in the first of the season’s two-day matches on Saturday.