Lomax, who has excelled in the absence of Kyle Eastmond, opened the scoring in the 4th minute after some neat footwork that left several Crusaders defenders floundering.
However home favourite Gareth Thomas touched down on 22 minutes to stem the flow and give the home fans something to cheer.
Their joy quickly turned to despair with Ade Gardner finding the stripe and Roby adding another try almost instantly as Saints went into the break 30-6 in front.
But any fears that Crusaders were on the way to yet another heavy defeat were to prove unfounded.
The hosts were much improved in the second period although Harris will be eager to address an obvious lack of direction in attack.
Lacking the fluency they displayed in the first half, Saints attempted to edge in front with a drop goal from Gaskell but his attempt drifted wide.
The home side’s inability to convert their possession into points was to prove costly as an excellent pass from Michael Shenton allowed Gardner to score his second try of the night in the final minute.
The result maintains St Helens recent improvement while reinforcing that Crusaders will have to pay far more attention to the bottom of the table than they did last season.
Crusaders: Schifcofske, Reardon, Martin, Thomas, Mellars, Witt, Hanbury, Bryant, White, Moore, Chan, Cahill, Johnson. Subs: Tansey, O’Hara, Flower, Winterstein.
St Helens: Wellens, Gardner, Shenton, Wheeler, Foster, Gaskell, Lomax, Perry, Roby, Graham, Puletua, Soliola, Flannery. Subs: McCarthy-Scarsbrook, Wilkin, Magennis, Makinson.
Goals: Jamie Foster (4, 8, 18, 28, 30)
Referee: Robert Hicks