Willetton found the spin of Kyle Millar too much to contend when he took 5-32.
The support of Matthew Dzodos’ 2-15 and Gary Atkinson’s 2-16 had the home team succumb for 93.
Mitch McGee, promoted after some second grade heroics, batted the innings to score an undefeated 40. Aaron Brunner was also undefeated on 39.
Wanneroo lost one wicket in securing the victory and second place on the competition ladder.
The side is expected to face Melville at Kingsway in the first grade qualifying final next Saturday and Sunday.
The Roos finished the season on 100 points, just 10 points behind minor premiers Claremont Nedlands.
The second grade side managed 180 in reply to Willetton’s 9-216 at Kingsway.
Jarred McPhee led the Wanneroo bowling when he took 3-45 and Graeme Atkinson was best with the bat when he scored a half century.
The side finished ninth for the season.
The third grade cricketers also missed the finals when they finished seventh.
A score of 102 at Burrandah 2 was not enough when Willetton lost six wickets in scoring 106 to take the victory.
The fourth grade side provided one of the highlights of the season for the club when it finished first on the premiership table.
The Roos became minor premiers when they dismissed Willetton for just 104 and lost five wickets in making 105.
Scott Pearson was again the leading bowler when he dismissed 3-12 while Aaron Fawcett took 3-24.
Best with the bat for Wanneroo was Bailey Nylander who made 32 and Cameron MacDonald who contributed 27.
Both the 15s and 17s failed to make the finals despite both teams defeating Willetton in the last qualifying game of the season.